Root cause:
"Bad Request" is an HTTP 400 returned by YouTube's player endpoint (youtube.com/youtubei/v1/player). The code in _download_webpage() raises RuntimeError(e.reason) on URLError, which propagates as the string "Bad Request" shown to the user.
Why only one user:
1. Expired/corrupt OAuth token — if previously logged into YouTube in the plugin and the refresh token stored on the receiver is now invalid, it gets sent as an Authorization header and YouTube rejects the whole request.
2. System clock out of sync — YouTube's API validates request timestamps; a receiver with a wrong clock can get 400s
3. Network/ISP interference — some ISPs or VPNs modify or block requests to YouTube's API endpoints
Possibe Fix (in order of likelihood):
1. Go into the YouTube plugin settings and sign out / clear the YouTube account — delete /etc/enigma2/YouTubeRefreshToken if it exists
2. Check and fix the receiver's system clock.
3. Try without VPN If a VPN is in use.