I think its more of a Samsung bug.. Have the same problem with my S5 sometimes the camera doesn't work with no reason the only solution to that is restarting the phone(after a few days the same problem occurs again). The only long-term solution is factory reset i don't want that too but restarting every few days is not a problem for me, but since u cant use your camera at all you have to reset it 0: use Samsung Kies to back up your messages,contacts,mediafiles,etc..
