Got camera back previous week. A new one actually, new box, everything exept battery. Had to order a new tempered glass protector as the one that died had it fixed when I sent it to service. Still got a couple of grips extra.
With regard to the issue:
Service were not able to detect moisture, cracks or whatsoever could have caused the camera to suddenly die.
Most likely cause which cannot be ruled out:
Overheating that made the PCB fail at some point, which was too minor to detect. Overheating could have been caused from WiFi tethering.
I know wifi tethering kills the battery too early, same hapening to my Lumix GX-80. However, the camera was only used to send ONE photo to my mobile, then I forgot Wifi on but unpaired my mobile, so it was on idle waiting for wifi connection (not longer than 20-25 minutes overall wifi) while we were browsing images in the KP's screen. Cannot be sure whether this caused so much overheating. Battery was cool when I extracted it to change it, so was the camera.
So, my thinking and doing from now on, very cautious use of the wifi with the Pentax KP, with parsimony, only on to share something, then off. That would be my advice to other Pentaxian folks as well!
I need to one more time thank the community for their support!