diff --git a/src/frontend/flask_app/blueprints/measure.py b/src/frontend/flask_app/blueprints/measure.py
index dc19562..5448d3b 100644
--- a/src/frontend/flask_app/blueprints/measure.py
+++ b/src/frontend/flask_app/blueprints/measure.py
@@ -440,7 +440,8 @@ def task_complete(recipe_id: int):
             m["subtask"] = st
             m["task_info"] = subtask_task_map.get(m.get("subtask_id"), {})
             # Compute deviation if not present
-            if m.get("deviation") is None and st.get("nominal") is not None:
+            # #118: quota non misurata (value None): la deviazione resta None (il template mostra NaN)
+            if m.get("deviation") is None and st.get("nominal") is not None and m.get("value") is not None:
                 try:
                     m["deviation"] = m["value"] - st["nominal"]
                 except (TypeError, KeyError):
diff --git a/src/frontend/flask_app/static/js/save_image.js b/src/frontend/flask_app/static/js/save_image.js
index a723490..49f0496 100644
--- a/src/frontend/flask_app/static/js/save_image.js
+++ b/src/frontend/flask_app/static/js/save_image.js
@@ -40,17 +40,22 @@ async function tmfBlobToPng(blob) {
 
 // #119: scarica `src`, lo porta a PNG e lo salva; true = salvato, false = annullato dall'utente o errore
 async function tmfSaveImage(src, baseName) {
+  if (!src) return false; // #119: nessuna immagine mostrata
   try {
+    var name = tmfSaveImageName(baseName, new Date());
+    // #119: «Salva con nome» per primo, finche' vale il gesto dell'utente (Chrome lo rifiuta dopo ~5 s di fetch e conversione)
+    var handle = null;
+    if (typeof window !== 'undefined' && typeof window.showSaveFilePicker === 'function') {
+      handle = await window.showSaveFilePicker({
+        suggestedName: name,
+        types: [{ description: 'PNG', accept: { 'image/png': ['.png'] } }],
+      });
+    }
     var resp = await fetch(src);
     if (!resp.ok) return false;
     var blob = await resp.blob();
     if (blob.type !== 'image/png') blob = await tmfBlobToPng(blob);
-    var name = tmfSaveImageName(baseName, new Date());
-    if (typeof window !== 'undefined' && typeof window.showSaveFilePicker === 'function') {
-      var handle = await window.showSaveFilePicker({
-        suggestedName: name,
-        types: [{ description: 'PNG', accept: { 'image/png': ['.png'] } }],
-      });
+    if (handle) {
       var w = await handle.createWritable();
       await w.write(blob);
       await w.close();