Question On Popping Sound

[caj]

I recently sold my accordion-reeded box to a friend, who says he's got a popping noise happens on 2 right-hand buttons, on the push.

 

I can't diagnose myself, and as this just arrived on my friend's doorstep I can't expect him to start doing surgery on the thing; I suspect from his description that the problem is a valve flapping shut audibly. As this is happening on the push, I guess it can't be anything flapping against a chamber wall.

 

My question is, if this is the problem what should I recommend as a remedy? Again, I don't think someone new to the concertina should have to start mucking about with adhesives. These are accordion reed blocks, screwed in place, so perhaps the best remedy is to simply ask the manufacturer for 2 new ones?

 

Caj