I still have the KP50, and recently having problems with batterry/heat.
Recently installed new CSSU update and bnf but it went fine for a few days.
(Read: I didn't yet updated to kp51 but have similair problem, i think it is not the case).
To prevent my device wear off I locked it to 500 and plugged out the cable. My batterry temperature dropped from 44 to safe 32 celsius but it discharged. Any help appreciated.