When I open the forum via my bookmark, this is what I see.
If I click on the 1, the page then loads OK.
We updated the forum a couple of weeks ago. This cache issue might be related, so maybe you should clear your web browser cache. Or at least try with another web browser to confirm it is an issue on your side.
Clearing the cache and restarting my browser did not help. Maybe it is a bug in the latest Vivaldi snapshot.
It seems to be a new bug in Vivaldi. If I zoom out, the text does not need to wrap so there is no overlay.
During the update we forgot to put back the older forum folders related to uploads of images and files from a decade ago. We have not restored it, so most images and files should now be available again in the older forum posts.