Calling Camera.Render() on a camera in LateUpdate() or PostLateUpdate() will either crop the sides of or completely erase the contents of the current quick menu tab.
When you open the menu the sides will be cropped.
If you switch to a different tab the contents there will display normally.
If you move to a different tab then close the menu and open it again, the menu will be completely empty.
The problem does not occur when called in Update().
Camera component settings do not matter.
The problem only occurs in VR.
There are a few other reports about avatars breaking when rendering cameras in LateUpdate/PostLateUpdate that have gone unresolved for years, but no mention of the menu breaking.
The problem has been present for at least half a year.
PC
VRChat build: 1801
SDK version: 3.10.2