This is a long-standing bug in the BBS that has been discussed in the past. No one has been able to track down its cause, and no one running other BBSs based on wwwthreads seems to be experiencing it.

It's not, to my knowledge, related specifically to a given forum. I have had it happen on every forum in the past.

Note that it seems to come and go in "waves" for a given user. For instance, I might have a period of a week where it happens to me, then it clears up for a long time. While things are working fine for me, some other users might report the bug.

Sometimes clearing your cache and cookies can help, but it does not solve the long-term problem.