I had a similar issue with the two Niwumpf boards i bought two years ago, every time i switched off then back on the high scores would reset to 320,000. i cant remember if anything else reset. both boards had the fault! Initially i thought it was a RAM problem too, (they have a 6116 RAM chip from memory) so i called Bumper action, who i bought them from and they asked me to send them back. apparently it turned out to be a software problem (thats what they told me) and they simply put an updated ROM into the boards. problem was solved. Maybe yours has a similar issue?