This happened to my Acadian made of "Red Pine" several years ago. It started with one flapper and then I noticed slight hesitation on two other flappers. It turned out that the flapper blocks had swollen around the metal rod that they pivot on. I removed the button board, pulled the rod out of the blocks with pliers, sanded the rod with fine sand paper to slightly reduce its diameter, reinserted the rod carefully back through the blocks, reattached some of the flapper springs that had come loose, reattached the button board and, voila!, no more sticking flappers. Steve
Just had the same problem after one gig in Vegas 2 weeks ago. Drastic weather change from Honolulu where I live. The problem fixed itself though without my having to do anything to the box. change from humid 85 to very dry 65 seemed to have had something to do with it. Back in Hawaii now with no sign of the problem at all.