Several times now i have had my character, and other enemies around me, disapear, as in, i cannot see them, at all. There is one case that i have found that during the college of winterhold questline, after entering Sarthal (the area, just after the draugr battle and Tolfdir tells you to go ahead) just as i walk through the doorway to the large room, that happens, it also happens to the draugr, i tried this several times, and when i made it to the stairs, my character and the draugr, all reapeared, turning around and going through the doorway again made me disapear again, i tried reloading a save from the excavation cell and going back in there, but it happened again.