Hi,
The only thing I can suspect now is the scrollbar script. It was recently added from the simplebar library. It may not calculate/update(?) the scroll area correctly, but I am sure there must be something else involved as well.
Do you happen to know, if you use any other scrollbar scripts by any chance (mCustomScrollbar, nicescroll or any others..)?
In the meantime, please try turning off the scrollbar script completely, you can do that here: https://i.imgur.com/VleAskD.png
I am just preparing an update for tomorrow, that includes a newer version of the scrollbar script, as well as some changes on how it’s handled. It may resolve that, if the issue is related to that.