Install folder changing location

Every once a while when I start the sim I’m greeted with “you have update” screen but the update is the whole game and target to install is somewhere on c: drive. If I point to the real install location (on a separate drive just for this game) it checks for updates, doesn’t find any problems and runs the game.
BUT! All graphics settings in game are messed up, probably set on default. And that requires setting everything up again and restarting a sim. Luckily keybinds remain untouched. Still it’s pain in the ■■■. What could cause this failed check on install location? How can I prevent this?