Have you ever asked a music / electronic store for a repair estimate? In my local area, for a small fee, a technician at a local repair shop will attempt, and almost always offer a solution to the problem. I'm
not that advanced technician guy, but to me it sounds like a flash memory burn out, and it may be repairable. That's just a guess, you need an expert to run physical tests to determine the exact cause of your problem.
In any case, nice to see someone can make some use of your "naughty 7000", and I suppose all Technics keyboards will eventually end up retiring to a similar fate, but for now, they just go on, and on, and on... Must have been built well.