Internal Server Error, no log

I got this error message, after running NC for several years via docker.

Internal Server Error

The server encountered an internal error and was unable to complete your request.
Please contact the server administrator if this error reappears multiple times, please include the technical details below in your report.
More details can be found in the server log.

However the error.log is zero bytes???

Did you already check in your data-dir for a .log file?