Oh yea some games do tend to move the start button. the general 'fix' is to change the game from 'fullscreen' to 'fullscreen(window)' if possible Or just restart classic shell when it happens.
I think its mostly on games whos resolution dont match that of the current desktop (windows DPI setting may have something to do with it too so setting that to 100% is something I would recommend if the game in question does use the same resolution as classic shell.
This bug has been part of classic shell for ages, and at this point I'm not banking on it ever getting fixed