I've let Peter know, there looks to be a server issue.
Damn.
I reloaded the software files and that seemed to resolve the issue. It almost seems that a file is getting corrupted. The actual PHP version is 8.3.x so the message is not really correct.
In any case there was also another upgrade of the site software that was released yesterday. After getting back into the system I installed that latest upgrade. I hope that resolves the issue.
