Internal Server Error after log in (backend still runnning and accessible)

I get an internal server error after tying to log in.
the backend (4443) is still accessbile and the raspi is also fin
Internal Server Error
The server was unable to complete your request.

If this happens again, please send the technical details below to the server administrator.

More details can be found in the server log.

Technical details
Remote Address:
Request ID: ZG@y0YZudS0@q6lXyem55AAAQws