[Q] Random shutdowns topic

have a t-mobile note 3, sm-n900t

twice now the phone has shutdown for no reason and i have to pull the battery to turn it back on. i've checked battery and both times it has had a 80%+ charge on it. has anyone else had this issue. if so what did you do to fix it. could it possibly be a nf9 firmware issue. i installed nk3 firmware. but run a nf9 rom. or is it a hardware issue. sorry if this has already been posted but i searched and found nothing. might not have used right search terms but i did search 1st