After I changed PHP version from 8.0 to 8.1, the forum on my website throws a “HTTP error 500” for foreign IP-numbers. A handful of users in Denmark also reports this error. The rest of the website works normal for all users. I can´t reproduce the error as I don´t get it:
https://www.jernbanen.dk/forum2/

Exact same problem on my swedish website, where the forum is blocked for a handful of users after switching to PHP 8.1:
https://www.svenska-lok.se/forum/

I have asked my webhotel (One.com) but with no reply yet.
Why do a handful of users get “HTTP error 500” just because I change PHP version from 8.0 to 8.1?

/Tommy