I see you made a comment in https://github.com/ValveSoftware/gamescope/issues/1913 . Did you try vkcube like someone earlier in that issue? And the other workarounds like --expose-wayland
?
Also what version of gamescope? And you don't happen to be running steam as a flatpak do you?
EDIT: they JUST released a new version https://github.com/ValveSoftware/gamescope/compare/3.16.14...3.16.15 . So if you are having issues downgrading might be worth a try, but I haven't been able to reproduce the issues you are having.
Also, I know it sounds weird for a linux machine, but update and restart just to rule anything weird out. I've had steam and steam related applications leave around weird state, processes, etc. before and restarting is an easy way to clear that all out and start fresh, eliminating variables.
You can do it just in the sketcher and get 90% of the way there with just sketcher constraints. You can also create a body with a subshape binder for each sketch line and use assembly and create an animation. You don't even need 3d solids. I created a gif, we'll see if it attaches properly to this reply...
Video: