This is not limited to the inventory. It's anything that has to scroll past a certain length. I am seeing this with PMs with more than 6 total messages included within the thread.
Elcysandir:
Sinya Arda:
Harandar:
I've circled date/time; URLs; the portion of the message showing where it's been cut off, even if that's just the buttons like in Harandar; and the bottom of the scroll bar to show that I can move no further down. I did black / blank out user names as they aren't relevant to the problem.
Access details:
Version: v1.137.2-(b5d0ba0) - html5 (2021-09-02 09:31)
World: Elcysandir, Sinya Arda, Harandar
Browser: Firefox 92.0.1 (64-bit)
OS: Win 10 64 Home
Screen resolution: 2560 x 1600
Account name: OIM20
Reproducibility: 4/5 = happens often, but not always -- seems to be related to the allowable length of the scroll bar.