Notifications seem to have this issue too. I have no idea what is causing the VRChat plus menu to appear on the right hand side, but I have also experienced instances of other menus appearing to the left. I was not able to obtain evidence of this, however. This issue seems to be fixed by selecting every menu one by one and then picking the one you want to look at.

Also pictured in the first screenshot is an issue with the quick menu not disappearing and remaining visible with no buttons, becoming a "phantom" quick menu.

I have not tested to see if these bugs are present on desktop.

Sorry about the low quality of my screenshots, this was the best I could do at the time.