Heads up Devs! When I entered the Forbidden Zone for the first time I was crouched down (for stealth). The game loaded me under the entrance stairs where I found myself stuck completely. Reloading auto save didn't fix so I had to use console commands to get unstuck. Just a warning to other players ... don't enter Forbidden Zone when crouched down.

This happened to me as well. Fortunately I had a quick save from just after leaving the nearby tunnel. When I next attempted to enter the facility I jumped and clicked to open the door and did not get trapped under the floor. I cleared the place and have returned to the faciltity on occasion but it has not re-occured.