Not knowing what "This thread" is or the new thread location. It is hard to tell.
Whenever you move a thread you have options to leave a pointer or not and for how many days.
Or could it be that selecting the post from say a side island is the problem.
I say that because they are cached and for a few moments may still point to a old location.
Till the cache gets rebuilt.
actual post urls may help a bit with troublshooting the issues.
Visiting your site as a guest I don't see a forum with 2005 in the name.
Last edited by Ruben; 08/17/2019 3:03 PM.