Sorry. Unfortunately, I can not reproduce this on another release. This is a production system which will be updated to 2.8.X “soon-ish”
Maybe someone else can verify/test if this happens with current release version, too. Or someone with great experience in the code can validate that this should not occur.
The interesting thing is, with some user accounts this issue occurs, with some others not. Can not find the cause why.
You could try safe mode[YourSite]/safe-mode with the themes and unofficial plugins disabled and see if that can narrow it down to one of them interfering?
Just noticed that I’m not facing this issue with Chromium. This could be a workaround for others.
My main browser is Firefox-esr (91.8.0esr) running on debian 11
I’m working together with @sbernhard at the same discourse instance (2.7.12) - as a moderator, I’m not a developer/admin. Until now, the “500 Internal Server Error” appeared at accounts with moderation rights. Normal users seemingly don’t get this error - they can access “Upcoming events” at the same moment, accounts with moderation rights is shown the error (at least, we didn’t receive other error reports yet).
As moderator, I get the error with Firefox 100, Edge 101 and up to date Chromium 101 on Windows 10 Pro, but as well on Ubuntu with Firefox. With a standard user account I don’t get the error on the same systems.