Sometimes that happens to me and if I have a second I go to change character screen and pick the same character and when it logs me back into the dungeon my stamina is working again.
You might have to try to talk to all the npcs in those lower levels, the quest icons don't show up over the npcs heads if your level is too high but they will still give you the quests.
Hi, I am having the same issue. I switched to my other character and tried to go to helms hold and back to fix it but the game froze while my second character was trying to travel to helms hold and now both characters loading screens freeze.