Can you please reupload the file
I re-uploaded it and still get the error. Every link in the admin area works except Forum Settings. I went from 2.4.18 to 2.4.19 I skipped 188.8.131.52
Ok, it was an attempt.
Also regular users are getting 500 errors sometimes clicking on bookmarks and sometimes selecting category.
You are sure, that this error did not occure before you updated your forum?
PS: I got an empty page (but no HTTP-status 500), when I opened the posting form to write this answer.
Trenne niemals Müll, denn er hat nur eine Silbe!