I manage 100+ iPads for my company. A 4th gen iPad battery has been rapidly draining and dead before end of the work day. I already reset it to factory settings and did everything related to decreasing battery drain (i.e. auto-lock at 2 minutes, screen brightness at half, kill apps not in use, disabled background app refresh, notifications disabled, bluetooth disabled, auto-brightness disabled). It is running iOS 10.1. Any suggestions on what I can try short of replacing this iPad???