I raised the height of the buttons on my second Acadian accordion the year I got it. I didn't do so with pieces of wood glued beneath the buttons (at first, I did that 8 years later). You can raise buttons with copper or brass rods, without any kind of elevating material for the buttons. That is, unless you want more height than you can naturally apply.

You must know how to properly bend the rods, to do this without any wood bits glued beneath the buttons.

On this accordion, I mention, button number nine would squeak slightly, and leak enough to bother me, no matter how I adjusted the copper rod, or fluffed up the felt of the flapper.

I can literally bend every single rod out of shape (within reason), on any accordion with copper rods, and fix it in at least 10 mins. In fact, I will take one of my accordions, bend all the rods out of shape, let you see how "screwed up" it is, and bend them back into shape. It's easy, as long as the ben is either top and bottom. Leaking sides take a bit more time to fix.

I'd also give you a vid of me doing this to aluminum rods (as many builders use), but those take much more time to fix. If they fix at all! Plus, aluminum breaks easy as ****, compared to copper or brass. May be prettier, and shinier, but I hate it.

Anyway, the mystery of button number nine leaking, is that the back of the button hole (closest to the faceplate), was a hair too close to the button itself. I've spent years trying to figure out what was wrong with it, and it was right there in front of my face. Just a little sanding of the hole

and all this time you have been unzipped showing your flapper

Seen a few times that holes widen slightly inwards on LA handmades .... thereby making smaller button holes possible. - Nout