I tried my best to replicate this issue, but was unable to. On my end it seems to be working fine. I unchecked all sub-forums except the EM forum, then refreshed the page and started scrolling. Everything was working fine.
Is there any way you could find out more, how to get this problem to occur? Also, when this happens, are you still signed in? I can imagine if your session cookie somehow gets removed that it might happen but thats just a wild guess.