Same Problem with Panasonic i have already solved.
1. clean the screen surface, it was formerly dirty by a thick layer of glue.
2. disconnect all internal Connectors.
3. clean all boards.
4. inspect the circuits by compare with original circuit sheet.
5. assembling again
After that the Error was vanish. I not know the source of problem but its work fine.
Some additional test show me:
The powercircuit have a sensible watchdog and shut down suddently if a fault detected.
1. my favorite suspection the glue on screen surface was keep some heat inside.
2. suspection some connector was have oxidation and disturb the the watchdog of powercircuit.
Warning: Danger for Life.
Open of this Device should only make by educated Electro Technican.