Just chiming in to say that I've also been experiencing this issue. It has been happening since INV 2021, (possible 2020 but I don't remember exactly).
Funny enough, I tried to use the autodesk screen capture software and when it loaded it said "Your current settings are not an optimal recording ratio, would you like to change?"
When I hit "yes", it resized my inventor window and the problem went away. This is when I realized that it only happens in full screen. When I switched back and forth to full screen, the problem would reproduce, but not in the "restored down" window.
You guessed it, yes, I do have an AMD card. I am using a Vega64.
Just to throw in another problem that I know crosses both AMD and Nvidia, is when Inventor is full screen, but a few pixels leak over to your second monitor. This can be fixed by directly snapping it to your monitor. (Drag the window all the way to the top of the screen until it "snaps")
I remember this issue being at least a few iterations old, possibly back to 2019. I'm the only AMD guy in my office, everyone else has NVIDIA. We all share this second problem, but not the first. The second issue has only been tested on 27" and 24" 16:9 monitors