Hello Guys,
FYI, I got exact same problem.
Battery level indicator freezing, never changed value till phone reboot.
uncontrolled reboot when plugged in in order to recharge. (mac or sector)
Solution:
Discovered that my Second hand iPhone had a chinese battery inside,...
After placing an certified battery inside, problem solved.
so,...
https://www.youtube.com/watch?v=JRMOMjCoR58
Cheers,