Error 500 on loading toolbar

Hello!
Since a few days I can not use the toolbar. The application works but there is a error 500 when the tollbar is called.

I can't insert a screenshot, so this is the awnser, copied from developers tool in FF

PHP Code:

HTTP/2 500 Internal Server Error
server: nginx
date: Thu, 06 Jan 2022 10:22:48 GMT
content-type: text/html; charset=UTF-8
content-length: 4393
cache-control: no-cache, no-store, must-revalidate
vary: Authorization
status: 500 Internal Server Error
X-Firefox-Spdy: h2 


I removed all collectors, to check where it comes from, but there is still error 500. Seems the core of the toolbar throws the error.

I also checked the logfiles but there is only a entry like in the networktraffic in developer toolbar.

So my idea was to open only the toolbar, hopefully it writes me a more helpful log. I opened "dashboard/?debugbar", which becomes "dashboard?debug" and a JS script appears. Thats it, no changes in my logfiles  

Some more investigation ideas???