Alas, I have to agree with that. I had a chance to handle the module from an HP01 at the last HPCC meeting. It consists of 2 ceramic 'circuit boards' glued together, the keyboard contacts being on the top one. I believe that inside, there are the bare silicon dice (chips), bonded out (connected) by fine gold wires to traces on the lower 'board'. These chips are not in packages, there's not way to replace them even if you could get spares (and AFAIK they were only used in the HP01). The display, battery contacts, crystal and a couple of passive components are soldered to the back surface of the lower board and could, in theory, be replaced, but they're unlikely to fail anyway.
The 2 boards are connected by a zebra-strip like connector on the right edge, which can be pulled out. This sowuld be worth cleaning if some of the keys are totally dead.
To return to the orignal problem, if this had been a classic-series machine (related architecture), I would have suspected a C&T chip failure, or maybe ROM failure. But there's no way to replace those on the '01