diff --git a/frontend/src/app/features/calculator/calculator-page.component.ts b/frontend/src/app/features/calculator/calculator-page.component.ts
index 9a57fc7..f40412b 100644
--- a/frontend/src/app/features/calculator/calculator-page.component.ts
+++ b/frontend/src/app/features/calculator/calculator-page.component.ts
@@ -48,7 +48,7 @@ export class CalculatorPageComponent implements OnInit {
 
     this.route.queryParams.subscribe(params => {
         const sessionId = params['session'];
-        if (sessionId) {
+        if (sessionId && sessionId !== this.result()?.sessionId) {
             this.loadSession(sessionId);
         }
     });
@@ -106,14 +106,14 @@ export class CalculatorPageComponent implements OnInit {
       forkJoin(downloads).subscribe({
           next: (results: any[]) => {
               const files = results.map(res => new File([res.blob], res.fileName, { type: 'application/octet-stream' }));
+              const colors = items.map(i => i.colorCode || 'Black');
               
               if (this.uploadForm) {
-                  this.uploadForm.setFiles(files);
+                  this.uploadForm.setFiles(files, colors);
                   this.uploadForm.patchSettings(session);
                   
                   // Also restore colors? 
-                  // setFiles inits with 'Black'. We need to update them if they differ.
-                  // items has colorCode.
+                  // setFiles inits with correct colors now.
                   setTimeout(() => {
                       if (this.uploadForm) {
                            items.forEach((item, index) => {
@@ -122,7 +122,11 @@ export class CalculatorPageComponent implements OnInit {
                                if (item.colorCode) {
                                    this.uploadForm.updateItemColor(index, item.colorCode);
                                }
+                               if (item.quantity) {
+                                   this.uploadForm.updateItemQuantityAtIndex(index, item.quantity);
+                               }
                            });
+                           this.uploadForm.updateItemIdsByIndex(items.map(i => i.id));
                       }
                   });
               }
@@ -164,6 +168,11 @@ export class CalculatorPageComponent implements OnInit {
             this.uploadProgress.set(100);
             this.step.set('quote');
 
+            // Sync IDs back to upload form for future updates
+            if (this.uploadForm) {
+                this.uploadForm.updateItemIdsByIndex(res.items.map(i => i.id));
+            }
+
             // Update URL with session ID without reloading
             if (res.sessionId) {
                 this.router.navigate([], {
@@ -200,10 +209,10 @@ export class CalculatorPageComponent implements OnInit {
     this.step.set('quote');
   }
 
-  onItemChange(event: {id?: string, fileName: string, quantity: number}) {
+  onItemChange(event: {id?: string, fileName: string, quantity: number, index: number}) {
       // 1. Update local form for consistency (UI feedback)
       if (this.uploadForm) {
-          this.uploadForm.updateItemQuantityByName(event.fileName, event.quantity);
+          this.uploadForm.updateItemQuantityAtIndex(event.index, event.quantity);
       }
       
       // 2. Update backend session if ID exists
diff --git a/frontend/src/app/features/calculator/components/quote-result/quote-result.component.html b/frontend/src/app/features/calculator/components/quote-result/quote-result.component.html
index f33740d..5a660a4 100644
--- a/frontend/src/app/features/calculator/components/quote-result/quote-result.component.html
+++ b/frontend/src/app/features/calculator/components/quote-result/quote-result.component.html
@@ -35,28 +35,37 @@
   
   <!-- Detailed Items List (NOW ON BOTTOM) -->
   <div class="items-list">
-    @for (item of items(); track item.fileName; let i = $index) {
-      <div class="item-row">
+    @for (item of items(); track item; let i = $index) {
+      <div class="item-row" [class.has-error]="item.error">
         <div class="item-info">
           <span class="file-name">{{ item.fileName }}</span>
-          <span class="file-details">
-             {{ (item.unitTime / 3600) | number:'1.1-1' }}h | {{ item.unitWeight | number:'1.0-0' }}g
-          </span>
+          @if (item.error) {
+            <span class="file-error">{{ 'CALC.ERROR_' + item.error | translate }}</span>
+          } @else {
+            <span class="file-details">
+                <span class="color-badge" [title]="item.color" [style.background-color]="getColorHex(item.color!)"></span>
+                {{ (item.unitTime / 3600) | number:'1.1-1' }}h | {{ item.unitWeight | number:'1.0-0' }}g
+            </span>
+          }
         </div>
         
         <div class="item-controls">
-            <div class="qty-control">
-                <label>Qtà:</label>
-                <input 
-                    type="number" 
-                    min="1" 
-                    [ngModel]="item.quantity" 
-                    (ngModelChange)="updateQuantity(i, $event)"
-                    class="qty-input">
-            </div>
-            <div class="item-price">
-                {{ (item.unitPrice * item.quantity) | currency:result().currency }}
-            </div>
+            @if (!item.error) {
+                <div class="qty-control">
+                    <label>Qtà:</label>
+                    <input 
+                        type="number" 
+                        min="1" 
+                        [ngModel]="item.quantity" 
+                        (ngModelChange)="updateQuantity(i, $event)"
+                        class="qty-input">
+                </div>
+                <div class="item-price">
+                    {{ (item.unitPrice * item.quantity) | currency:result().currency }}
+                </div>
+            } @else {
+                <div class="item-price error">-</div>
+            }
         </div>
       </div>
     }
diff --git a/frontend/src/app/features/calculator/components/quote-result/quote-result.component.scss b/frontend/src/app/features/calculator/components/quote-result/quote-result.component.scss
index c9f6973..afc1e0d 100644
--- a/frontend/src/app/features/calculator/components/quote-result/quote-result.component.scss
+++ b/frontend/src/app/features/calculator/components/quote-result/quote-result.component.scss
@@ -21,6 +21,11 @@
     background: var(--color-neutral-50);
     border-radius: var(--radius-md);
     border: 1px solid var(--color-border);
+    
+    &.has-error {
+        border-color: #ef4444;
+        background: #fef2f2;
+    }
 }
 
 .item-info {
@@ -31,7 +36,21 @@
 }
 
 .file-name { font-weight: 500; font-size: 0.9rem; color: var(--color-text); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
-.file-details { font-size: 0.8rem; color: var(--color-text-muted); }
+.file-details { 
+    font-size: 0.8rem; 
+    color: var(--color-text-muted); 
+    display: flex;
+    align-items: center;
+    gap: var(--space-2);
+}
+.color-badge {
+    width: 10px;
+    height: 10px;
+    border-radius: 50%;
+    border: 1px solid var(--color-border);
+    display: inline-block;
+}
+.file-error { font-size: 0.8rem; color: #ef4444; font-weight: 500; }
 
 .item-controls {
     display: flex;
diff --git a/frontend/src/app/features/calculator/components/quote-result/quote-result.component.ts b/frontend/src/app/features/calculator/components/quote-result/quote-result.component.ts
index 8d3e193..e507e43 100644
--- a/frontend/src/app/features/calculator/components/quote-result/quote-result.component.ts
+++ b/frontend/src/app/features/calculator/components/quote-result/quote-result.component.ts
@@ -6,6 +6,7 @@ import { AppCardComponent } from '../../../../shared/components/app-card/app-car
 import { AppButtonComponent } from '../../../../shared/components/app-button/app-button.component';
 import { SummaryCardComponent } from '../../../../shared/components/summary-card/summary-card.component';
 import { QuoteResult, QuoteItem } from '../../services/quote-estimator.service';
+import { getColorHex } from '../../../../core/constants/colors.const';
 
 @Component({
   selector: 'app-quote-result',
@@ -18,11 +19,13 @@ export class QuoteResultComponent {
   result = input.required<QuoteResult>();
   consult = output<void>();
   proceed = output<void>();
-  itemChange = output<{id?: string, fileName: string, quantity: number}>();
+  itemChange = output<{id?: string, fileName: string, quantity: number, index: number}>();
 
   // Local mutable state for items to handle quantity changes
   items = signal<QuoteItem[]>([]);
 
+  getColorHex = getColorHex;
+
   constructor() {
       effect(() => {
           // Initialize local items when result inputs change
@@ -44,7 +47,8 @@ export class QuoteResultComponent {
       this.itemChange.emit({
           id: this.items()[index].id,
           fileName: this.items()[index].fileName,
-          quantity: qty
+          quantity: qty,
+          index: index
       });
   }
 
diff --git a/frontend/src/app/features/calculator/components/upload-form/upload-form.component.html b/frontend/src/app/features/calculator/components/upload-form/upload-form.component.html
index eba5371..c9775f4 100644
--- a/frontend/src/app/features/calculator/components/upload-form/upload-form.component.html
+++ b/frontend/src/app/features/calculator/components/upload-form/upload-form.component.html
@@ -25,7 +25,7 @@
     <!-- New File List with Details -->
     @if (items().length > 0) {
         <div class="items-grid">
-            @for (item of items(); track item.file.name; let i = $index) {
+            @for (item of items(); track item; let i = $index) {
                 <div class="file-card" [class.active]="item.file === selectedFile()" (click)="selectFile(item.file)">
                     <div class="card-header">
                         <span class="file-name" [title]="item.file.name">{{ item.file.name }}</span>
diff --git a/frontend/src/app/features/calculator/components/upload-form/upload-form.component.ts b/frontend/src/app/features/calculator/components/upload-form/upload-form.component.ts
index 9258067..d407b69 100644
--- a/frontend/src/app/features/calculator/components/upload-form/upload-form.component.ts
+++ b/frontend/src/app/features/calculator/components/upload-form/upload-form.component.ts
@@ -12,6 +12,7 @@ import { QuoteRequest, QuoteEstimatorService, OptionsResponse, SimpleOption, Mat
 import { getColorHex } from '../../../../core/constants/colors.const';
 
 interface FormItem {
+    id?: string;
     file: File;
     quantity: number;
     color: string;
@@ -178,6 +179,37 @@ export class UploadFormComponent implements OnInit {
       });
   }
 
+  updateItemQuantityAtIndex(index: number, quantity: number) {
+      this.items.update(current => {
+          const updated = [...current];
+          if (updated[index]) {
+              updated[index] = { ...updated[index], quantity };
+          }
+          return updated;
+      });
+  }
+
+  updateItemIds(itemsWithIds: { fileName: string, id: string }[]) {
+      this.items.update(current => {
+          return current.map(item => {
+              const match = itemsWithIds.find(i => i.fileName === item.file.name && !i.id); // This matching is weak
+              // Better: matching should be based on index if we trust order
+              return item;
+          });
+      });
+  }
+
+  updateItemIdsByIndex(ids: (string | undefined)[]) {
+      this.items.update(current => {
+          return current.map((item, i) => {
+              if (ids[i]) {
+                  return { ...item, id: ids[i] };
+              }
+              return item;
+          });
+      });
+  }
+
   selectFile(file: File) {
       if (this.selectedFile() === file) {
           // toggle off? no, keep active
@@ -208,11 +240,7 @@ export class UploadFormComponent implements OnInit {
       let val = parseInt(input.value, 10);
       if (isNaN(val) || val < 1) val = 1;
       
-      this.items.update(current => {
-          const updated = [...current];
-          updated[index] = { ...updated[index], quantity: val };
-          return updated;
-      });
+      this.updateItemQuantityAtIndex(index, val);
   }
 
   updateItemColor(index: number, newColor: string) {
@@ -234,12 +262,12 @@ export class UploadFormComponent implements OnInit {
       });
   }
 
-  setFiles(files: File[]) {
+  setFiles(files: File[], colors?: string[]) {
       const validItems: FormItem[] = [];
-      for (const file of files) {
-          // Default color is Black or derive from somewhere if possible, but here we just init
-          validItems.push({ file, quantity: 1, color: 'Black' });
-      }
+      files.forEach((file, i) => {
+          const color = (colors && colors[i]) ? colors[i] : 'Black';
+          validItems.push({ file, quantity: 1, color: color });
+      });
 
       if (validItems.length > 0) {
           this.items.set(validItems);
diff --git a/frontend/src/app/features/calculator/services/quote-estimator.service.ts b/frontend/src/app/features/calculator/services/quote-estimator.service.ts
index 93a5f80..35c8cdf 100644
--- a/frontend/src/app/features/calculator/services/quote-estimator.service.ts
+++ b/frontend/src/app/features/calculator/services/quote-estimator.service.ts
@@ -26,6 +26,7 @@ export interface QuoteItem {
   quantity: number;
   material?: string;
   color?: string;
+  error?: string;
 }
 
 export interface QuoteResult {
@@ -255,11 +256,22 @@ export class QuoteEstimatorService {
              let validCount = 0;
 
              responses.forEach((res, idx) => {
-                 if (!res || !res.success) return;
-                 validCount++;
+                 const quantity = res?.originalQty || request.items[idx].quantity || 1;
                  
+                 if (!res || !res.success) {
+                     items.push({
+                         fileName: request.items[idx].file.name,
+                         unitPrice: 0,
+                         unitTime: 0,
+                         unitWeight: 0,
+                         quantity: quantity,
+                         error: res?.error || 'UPLOAD_FAILED'
+                     });
+                     return;
+                 }
+                 
+                 validCount++;
                  const unitPrice = res.unitPriceChf || 0;
-                 const quantity = res.originalQty || 1;
                  
                  items.push({
                      id: res.id,
@@ -270,8 +282,6 @@ export class QuoteEstimatorService {
                      quantity: quantity,
                      material: request.material,
                      color: res.originalItem.color || 'Default'
-                     // Store ID if needed for updates? QuoteItem interface might need update
-                     // or we map it in component
                  });
                  
                  grandTotal += unitPrice * quantity;
diff --git a/frontend/src/app/features/contact/components/contact-form/contact-form.component.html b/frontend/src/app/features/contact/components/contact-form/contact-form.component.html
index b0f7bed..3119dab 100644
--- a/frontend/src/app/features/contact/components/contact-form/contact-form.component.html
+++ b/frontend/src/app/features/contact/components/contact-form/contact-form.component.html
@@ -37,20 +37,20 @@
       <app-input formControlName="companyName" [label]="('CONTACT.COMPANY_NAME' | translate) + ' *'" [placeholder]="'CONTACT.PLACEHOLDER_COMPANY' | translate"></app-input>
       <app-input formControlName="referencePerson" [label]="('CONTACT.REF_PERSON' | translate) + ' *'" [placeholder]="'CONTACT.PLACEHOLDER_REF_PERSON' | translate"></app-input>
     </div>
-    
+
     <div class="form-group">
       <label>{{ 'CONTACT.LABEL_MESSAGE' | translate }}</label>
-      <textarea formControlName="message" class="form-control" rows="4"></textarea>
+      <textarea formControlName="message" class="form-control" rows="10"></textarea>
     </div>
 
     <!-- File Upload Section -->
     <div class="form-group">
       <label>{{ 'CONTACT.UPLOAD_LABEL' | translate }}</label>
       <p class="hint">{{ 'CONTACT.UPLOAD_HINT' | translate }}</p>
-      
-      <div class="drop-zone" (click)="fileInput.click()" 
+
+      <div class="drop-zone" (click)="fileInput.click()"
            (dragover)="onDragOver($event)" (drop)="onDrop($event)">
-        <input #fileInput type="file" multiple (change)="onFileSelected($event)" hidden 
+        <input #fileInput type="file" multiple (change)="onFileSelected($event)" hidden
                accept=".jpg,.jpeg,.png,.pdf,.stl,.step,.stp,.3mf,.obj">
         <p>{{ 'CONTACT.DROP_FILES' | translate }}</p>
       </div>
diff --git a/frontend/src/assets/i18n/en.json b/frontend/src/assets/i18n/en.json
index 22dbba7..2b5a432 100644
--- a/frontend/src/assets/i18n/en.json
+++ b/frontend/src/assets/i18n/en.json
@@ -61,6 +61,9 @@
     "ORDER": "Order Now",
     "CONSULT": "Request Consultation",
     "ERROR_GENERIC": "An error occurred while calculating the quote.",
+    "ERROR_UPLOAD_FAILED": "Calculation failed",
+    "ERROR_VIRUS_DETECTED": "File removed (virus detected)",
+    "ERROR_SLICING_FAILED": "Slicing error (complex geometry?)",
     "NEW_QUOTE": "Calculate New Quote",
     "ORDER_SUCCESS_TITLE": "Order Submitted Successfully",
     "ORDER_SUCCESS_DESC": "We have received your order details. You will receive a confirmation email shortly with the payment details.",
diff --git a/frontend/src/assets/i18n/it.json b/frontend/src/assets/i18n/it.json
index 9597eed..b8d0504 100644
--- a/frontend/src/assets/i18n/it.json
+++ b/frontend/src/assets/i18n/it.json
@@ -40,6 +40,9 @@
     "ORDER": "Ordina Ora",
     "CONSULT": "Richiedi Consulenza",
     "ERROR_GENERIC": "Si è verificato un errore durante il calcolo del preventivo.",
+    "ERROR_UPLOAD_FAILED": "Calcolo fallito",
+    "ERROR_VIRUS_DETECTED": "File rimosso (virus rilevato)",
+    "ERROR_SLICING_FAILED": "Errore slicing (geometria complessa?)",
     "NEW_QUOTE": "Calcola Nuovo Preventivo",
     "ORDER_SUCCESS_TITLE": "Ordine Inviato con Successo",
     "ORDER_SUCCESS_DESC": "Abbiamo ricevuto i dettagli del tuo ordine. Riceverai a breve una email di conferma con i dettagli per il pagamento.",