I can see through walls all of the time. How can I fix this?

[Romulator]

You won't lose your save file since the game's saves are stored on the cloud servers - as well as away from your installation.

You may not need to reinstall, my best guess is the game failed to preload assets or has not run a particular script to load the environment correctly. The first thing to try would be to load a slightly older save from the "Load Game" option in the menu. If the problem persists, try a Steam File Integrity Check (if you are using Steam) in the possibility you're missing assets or certain files needed to create the environment.