It is because as some point, the electrical connection is intermittently broken. That could be the switch button or corroded battery contacts, but it could also be some other point in the circuit. I don't know about the Planet Bike Blinky Superflash specifically, but any time the circuit includes part of the body, that's the weak link. That would be the case if the switch can be separated from the light or LED. Clean that part, use sandpaper even, if there is someplace that aluminum joins.