Hammer & Sustain Problems = Loose Assembly?
Hammers are too loose, wobbling and even breaking? Sustain feels uneven and unaccurate? Check that the keyboard assembly sits firmly and correctly in the cabinet.
In some pianos, hammers suddenly can start to wear fast and break. Since the ABS teflon flanges are made to last a piano's lifetime, one now must suspect that something has happened physically to the assembly. Always start this check by removing lid, harp, damper release bar, namerail and all the keys.
Now you can inspect the assembly and check that it is firmly attached to the cabinet, and that the four screws that hold it are tight and intact. I always make this extra sure by drilling an extra screw downwards, under the keys, in the middle of the piano. Check this by trying to lift the assembly up from the lid.
If there has been damage to the screws or something else has happened that makes the assembly loose, it almost certainly has caused the hammer rail to bend and wobble during transport and playing. This quickly wears the hammers out, since they now strike unevenly and are "wobbly".
If a loose assembly hasn't caused it, the problem can also be cracks in the plastic hammer combs or "multiple flanges" the hammers sit in. This also makes the hammers go back and forth and eventually snap. Replacement is the only solution to this. Also be aware that, although the flanges are able to last for years and years, they can also be quickly ruined by tightening the screws that hold them too tight!
As long as the two above-mentioned scenarios are taken care of, there shouldn't be any more problems with hammers breaking or any other strange behaviour of the hammers. You're now ready to replace damaged parts and get into the fun of optimizing and fine-tuning your pride and joy!