As Mark C indicated, assuming the pinblock is not cracked...
You could also try:
Max's cardboard shims
These would be even less expensive than replacing the tuning pins.
These may not be permanent, of course. But, they may be useful as a diagnostic tool. If neither of these helps, then there is a bigger problem.. probably with the pinblock.
I am very concerned that the CA repair did not last very long on either piano.
Are the bass pins that do hold jumpy? Before applying the CA glue, did you observe any sort of discoloration on the plate near the bass tuning pins?
I am wondering if the pinblock itself might be contaminated with something.
Maybe someone with a can of WD-40 who sprayed the nut thinking it would help the strings render easier? Then, the over-spray got to the pinblock.
It's also possible that someone may have been a bit overzealous about cleaning the piano. I've seen customers open the lid of a vertical piano and then apply a very generous amount of furniture oil to the top of the pinblock/core in order to clean it (before I could stop them). Not only can the oil wick into the wood if the top of the pinblock is exposed, but the oil can run between the pinblock and the plate.
This seems possible to me. The bass pins will be closer to the top than most of the tenor/treble pins. So, furniture oil can reach these pins more easily.
I think the key is whether or not the other pins in the area are jumpy.
This is only speculation, of course.
Could there be some sort of ongoing external problem, such as the sun beating down on the back of the piano on the bass end? Or, maybe the piano has a heat source behind it or beside it, such as a heating duct or steam radiator?
Edit: Do you see any finish damage on the bass side of the piano, or on the back of the piano? Is it a "striped" piano?
Last edited by daniokeeper; 09/24/15 03:29 AM.