Videos named as "videoplayback"

Hi,

I use to download videos from YouTube and get them with their original title. Now, whatever I download, all the videos are named "videoplayback". I uninstalled and reinstalled, but nothing changed. Here are my specs :

• Browser: Safari 14.0.3 Mac OS X
• User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0.3 Safari/605.1.15
• Extension: userjs-safari 9.51.2

Thank you if you can find where is this issue from.