Help on repairs!!

[JSmith3109@AOL.COM]

Dear list:

The piano is a Cable-Nelson Ser.#316422 (1948-49) I have tuned the piano for 
about 10 years. Many times they call me about keys that do not work. Mainly 
in octaves 4 and 5 (F#-A-4: G-A#-5) The problem: The keys will work several 
times, then the jack fails to return under the hammer butt. If you work at a 
little it will go back under and then work for several more times (maybe 
15-20, maybe 2 weeks).I have adjusted the regulating screw, the capstan, 
replaced the jack springs,adjusted the spoon,used Protek on the key, 
re-pinned the flanges, checked the key bushings,but still they refuse to work 
as they should. What am I missing? The piano is not abused as it it used by 3 
girls in the family that are serious about the piano and do a lot of 
practicing. I would like to try something else so that I can leave the house 
and feel confident that the keys will work for the kids.