HTC One M8 woes

Hi guys
Got a HTC One M8 off my sister, the phone will only boot in safe mode. The vol down key also seems not to work even though there appears no damage to the button. I've factory reset it and got the same, and its got the latest software when i try to auto update. any ideas? its doing my head in as in safe mode only the stock apps appear, even though it keeps kindly updating my apps and letting me know Thanks in advance

Could try this,
1: Restart holding power and volume up buttons.
2: With phone powered on, press and hold power button to bring up "Power Options" menu. Choose restart.
The volume down button could also be stuck on, in which case phone will always start in safe mode.
good luck.