[ujiro]

Yeah that was going to be my next thought. Could be its somehow not releasing right away. But that also sounds like something that would be intermittent and/or would be fixed after a few shots as it would bend back into shape. Although actually if the plastic carrier/follower was out of shape, I suppose it could easily be caught on its way back and stay held with the switch closed... Check the mobility of the switch then too, when you pull the trigger then release.