Originally posted by Mikhail_Kriviniouk update - my k5 came back to life. further info - I seem to have established that if the voltage on the battery's terminals is below 8.1V the multiple mirror slap cannot be repeated... if you exchange the battery for a freshly charged one (8.4V), then It might do it. This is regardless of where the battery is and which one is used - body or grip. If there is a battery in the system with voltage higher than whatever - problems will be there. Under 8.1V and the weird behaviour can't be repeated.
Update: mine died again yesterday. nothing I tried makes the mirror go up or the shutter to open (release/ fire); everything else functions, inc. AF, viewing, editing etc, but the camera would not take a shot.