Quoted from german-pinball:
Typical system3-problem!!! Change capacitors C20 + C21 and you will be happy again. From factory both are 1uF Tantal-capacitors, but you can take as an alternative two "normal" electrolytic capacitors 1uF 20V.
I just fixed my Shaq with the exact same problems by doing this. Apparently the caps are all dying at the same time.