HP-97 keyboard problem

[Dave92F1]

I just got my 3rd HP-97 from eBay. Two rows on the keyboard don't seem to register.

The digits 1, 2, 3 and the whole row ENTER/CHS/EEX/divide do nothing at all when I press them.

Other than that the calculator seems OK (didn't test the printer or card reader yet; I suppose they'll need the usual...)

I already completely disassembled and cleaned the keyboard and key contacts - that didn't help (didn't make it worse either). I also checked the connection on the pins in connectors P1 and P2 carefully - that doesn't seem to be it either. I tested with a known-good battery pack and charger from another HP-97.

Any suggestions?

If I can't get it working, I'll have to sell it for parts and buy another one (I actually use these things!)