Try to prevent caching of placeholder

app.py

@@ -307,6 +307,9 @@ def cdn_redirect(video_id):
     logger.info(f"{video_id}: Video not found in CDN, returning placeholder")
     response = make_response(send_file(BytesIO(placeholder_video), mimetype="video/mp4"))
     response.headers['Content-Length'] = str(len(placeholder_video))
+    response.headers['Cache-Control'] = 'no-cache'
+    response.headers['Pragma'] = 'no-cache'
+    response.headers['Expires'] = '0'
     return response