At base camp,the place you go after every mission, there is a house, upstairs in that house there is a pot of yellow mushrooms. Climb up a slab next to the wall, and then up onto the pot of mushrooms behind there is a small gap you can slip into and fall into a small hole. There you will be stuck and the only way out is by restarting your game! Please remove the small gap. Also this is only one spot I found to get stuck in, please make sure there are no spots that you can get stuck in!