Over the last couple of weeks, I've noticed a recurring problem, which has happened once again today. The air button on my Mengascini suddenly starts to click and then gets jammed open. When opening the bass end and having a fiddle, the problem is obvious - the the wooden block and pad that covers the hole has moved slightly and is getting stuck on a wood ledge at the corner of the casing. The only reason I can find that suggests why this is happening is that the wax holding the block in position is sometimes getting soft (from the heat...), thus allowing the the block to travel along the metal arm that it's attached too and consequently ending up out of place.
It's easy to fix the problem temporarily - just move the block back along the arm. But what's to stop it happening again? Is there anything that can be done to avoid the problem in the first place?