I usually just look at the EM forums, so I select just those to view.
If I'm not on Pinside for a few days, when I enter pinside forums, the first "page" will show only posts from the desired EM forums, but the 2nd "page" will show posts from all the forums. Page 3, 4, etc, will continue to show posts from all the forums.
The only way I've found to reset the sub-forum filtering is to logout, exit Chrome and then re-login. The forum viewer will work ok and then a few days later the problem will re-occur.
This started about 6+ months ago.
Attached is a section from a screen shot.Pinside (resized).PNG
--------------------------------
Your browser/os information:
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.96 Safari/537.36 (this will help us make sense of your bug report)
Pinside (resized).PNG