There seems to be a bug where if the player gets underneath anything hanging down from above, like branches. When that happens, the player cannot stand up, or is immobilized. I first noticed this when crouch-walking past enemies to avoid detection. If I WAS detected, I immediately would start sprinting away. This does not work when creeping through low hanging branches. This is also a problem when prone and creeping though low branches. The branches prevent the player from standing up.