When PNL fixed two of my MS2930 boards that had this exact issue, they said it was the "HV Circuit". They wouldn't really tell me what in the HV Circuit went bad though.
I got one of the chassis going. Followed the service manual for the 2931 and had a faulty u701 (the little daughter board). Now I have weird bleeding/colour issue. So far I replace the neck board and I'll let you know what I find out.