I had this also once with V3 after 3 days without booting. Phone froze I had to press power button for 10 sec to force reboot.....Seems like phone's hardware malfunction. Try to go to TWRP recovery and flash ROM and gapps again. This time do a factory reset before flashing. If you face similar problem go back to your previous ROM and test.
But now with V4 the standby battery is really great:
Gesendet von meinem LeTv 1 Pro mit Tapatalk

