It happens after the second room that has the statue of the demon talking directly to our mind. After the fight against the illusions finishes and the player is allowed to move again, they're stuck facing forward (also, the stairs can be used in the stuck state, you just need to hit the interact key when on the tile with the actual stair visuals (the "open pit" side only sometimes does the "autodrop and deal damage" thing, but the "stair visuals" side will do nothing unless the interact key is hit when standing on top of them.) In regards to fixes outside of the debugger menu, I've found that attempting to walk into the first statue room that became the nun room will fix it (the forced backwards movement from that seems to fix whatever trigger for rotation wasn't working right with the 2nd statue room)).