Hi, Stefan. Sorry you’re experiencing this.
This isn’t currently a known issue, and I didn’t get debug messages when visiting one of my site’s event category pages, so I’d suggest following these recommended troubleshooting steps for your own site:
I see you’re already using the latest versions of WordPress core and our pluings. That’s great. Please follow our Testing for Conflicts Guide (basically switch to Twenty Seventeen theme and deactivate all plugins and custom code other than Modern Tribe plugins) and see if that helps narrow down the cause of this.
Of course, we always recommend restorable database and file backups before modifying anything on your site.
If it doesn’t, please enable WP_DEBUG and WP_DEBUG_LOG (which will create a file on your server at /wp-content/debug.log if there are any WP_DEBUG messages) and share any debug messages you see while trying to replicate this issue and doing other things on your site relevant to this ticket (such as visiting your site’s home page, events page, single-event pages, and anything else you can think to do).
Then, please re-share your System Information (while in Testing for Conflicts Mode) in a Private Reply. That will give me a lot of extra information to help troubleshoot this.
Let us know what you find out.
Thanks.