Gamebreaking Invisible Walls in Theta Maintenance

[idk303]

I am experiencing a gamebreaking bug that occurs after the cutscene in which you are grabbed by the monster that runs down the stairs in Theta Maintenance. After that sequence, all of the area's walls are invisible, making it effectively impossible to navigate the area. How can I fix this?

[Romulator]

Perform a Steam File Integrity Check if you are using Steam. If you are using GOG, repair your installation. Then reload a slightly earlier save using the Load Game option from the menu.