Unfortunately this tends to happen eventually. The triggers pushing down on the foam pad over and over just wears it out and causes it to come away from the adhesive. I personally replace them with strips of 1mm thick solid neoprene rubber. It's much firmer so it doesn't squish and break like the foam they use from the factory. Not a big deal though as you can just do what you showed and clean off the adhesive and leave the rubber off. I like the cushioning feeling though personally.
