I would take it apart just to see what's what, because the same thing happening to me. I took mine apart and found the screw/nut that keeps the metal clip fastened was loosening up (the metal clip being the "spring" that keeps the battery in place). A very simple tightening of the screw fixed the problem, and viola.
If you do decide to go down the Pila USA route, they will take care of you. Ken and Mary are very nice people and service is #1.