Unfortunately this is a rare, but known issue with the game. You will have to make a clean installation of the game.
- If you are using Galaxy, please select the game in Galaxy, click on More -> Manage Installation -> Uninstall. After removing the game install it once again.
- If the game was installed using offline installer, then please press WinKey+R to open Run window, and here type:
and press Ok. Once in Programs & Features find and uninstall the game. After that download and install the latest version of the base installer from your GOG account: