diff --git a/deploy-frontend.sh b/deploy-frontend.sh
index 3ad9b70..940258c 100755
--- a/deploy-frontend.sh
+++ b/deploy-frontend.sh
@@ -57,9 +57,12 @@ echo "✅ Build erfolgreich!"
 echo "Erstelle Zielverzeichnis..."
 sudo mkdir -p /opt/yourpart/frontend/dist
 
-# 7. Altes Frontend löschen
-echo "Lösche altes Frontend..."
-sudo rm -rf /opt/yourpart/frontend/dist
+# 7. Sicheres Backup des alten Frontends (timestamped). Vermeidet Datenverlust bei Fehlern.
+if [ -d "/opt/yourpart/frontend/dist" ]; then
+  TIMESTAMP=$(date +%Y%m%d-%H%M%S)
+  echo "Erstelle Backup von altem Frontend nach /opt/yourpart/frontend/dist.backup.$TIMESTAMP"
+  sudo mv /opt/yourpart/frontend/dist /opt/yourpart/frontend/dist.backup.$TIMESTAMP || true
+fi
 
 # 8. Zielverzeichnis neu erstellen
 echo "Erstelle Zielverzeichnis neu..."
diff --git a/frontend/src/dialogues/socialnetwork/VocabPracticeDialog.vue b/frontend/src/dialogues/socialnetwork/VocabPracticeDialog.vue
index 8988a9e..0b816d1 100644
--- a/frontend/src/dialogues/socialnetwork/VocabPracticeDialog.vue
+++ b/frontend/src/dialogues/socialnetwork/VocabPracticeDialog.vue
@@ -697,24 +697,35 @@ export default {
       return [{ ...item, learning, reference }];
     },
     normalizePool(items = []) {
-      const seen = new Set();
-      return (Array.isArray(items) ? items : [])
-        .flatMap((item, index) => this.expandPoolItemAlternatives(item).map((candidate, altIndex) => ({ candidate, index, altIndex })))
-        .map(({ candidate, index, altIndex }) => {
-          const learning = String(candidate?.learning || '').trim();
-          const reference = String(candidate?.reference || '').trim();
-          if (!this.isTrainablePair(learning, reference)) return null;
-          const key = `${this.normalize(learning)}|${this.normalize(reference)}`;
-          if (seen.has(key)) return null;
-          seen.add(key);
-          return {
-            ...candidate,
-            id: candidate?.id || candidate?.itemKey || candidate?.key || `${key}|${index}|${altIndex}`,
-            learning,
-            reference
-          };
-        })
-        .filter(Boolean);
+      try {
+        const inputLen = Array.isArray(items) ? items.length : 0;
+        const seen = new Set();
+        const expanded = (Array.isArray(items) ? items : [])
+          .flatMap((item, index) => this.expandPoolItemAlternatives(item).map((candidate, altIndex) => ({ candidate, index, altIndex })));
+
+        const mapped = expanded
+          .map(({ candidate, index, altIndex }) => {
+            const learning = String(candidate?.learning || '').trim();
+            const reference = String(candidate?.reference || '').trim();
+            if (!this.isTrainablePair(learning, reference)) return null;
+            const key = `${this.normalize(learning)}|${this.normalize(reference)}`;
+            if (seen.has(key)) return null;
+            seen.add(key);
+            return {
+              ...candidate,
+              id: candidate?.id || candidate?.itemKey || candidate?.key || `${key}|${index}|${altIndex}`,
+              learning,
+              reference
+            };
+          });
+
+        const result = mapped.filter(Boolean);
+        try { console.debug('[VocabPracticeDialog] normalizePool', { inputLen, outLen: result.length, sample: result.slice(0,5) }); } catch (_) {}
+        return result;
+      } catch (e) {
+        console.warn('[VocabPracticeDialog] normalizePool failed', e);
+        return [];
+      }
     },
     resetQuestion() {
       this.current = null;