[ Ref. Philip Carli in 231023 MMDigest ]

Check [for leakage] at least five of the note valves in the middle
of the stack. Take out the metal poppet cover and test the adhesive
security of the internal black Bakelite seat by using an "L" shaped
hook. If any [valve seats] come out, or even fall out with no
encouragement, the course of action is clear: _all_ must be removed
and reglued.

I use #320 plastic glue (or equivalent) because it will "give and
take" with temperature and humidity swings, whereas the original
adhesive (shellac) cracks and loosens with these swings (as well
as with normal aging). If any break during this process, I can
3-D print them in a robust plastic material.

John Grant
Baltimore, Maryland