What works really well is very thin "Crazy Glue" that is as thin as
water.  You can buy it at any hobby shop.  I use a piano tipper and
lay the piano on its back and with a syringe put a few drops of glue
down around the pin.  It will not lock the pin but will expand the
wood, tightening the pin. I used this method on a dominion upright
player piano.

Hope that helps.

David Dunn
Morden, Manitoba, Canada