Interested to see how this concludes. I have similar issues with my silverball.Was planning on repinning boards(have the parts,just have not done anything more) and doing the ground mods.My symptoms are similar other than on reboot it changes some settings like replay score and game credits at random.My MPU did have an acid issue before I got it.I attempted to change credits via dip switch but it would not change the setting
Good luck.