Update app.py

app.py

@@ -176,6 +176,9 @@ def prepare_download():
 
 
 def get_first_group():
+    global preloaded_until
+    preloaded_until = PRELOAD_AHEAD - 1  # 🛠 Reset preload window
+
     reviewed, remaining = get_remaining_groups()
     current_index = 0