I could be wrong about the o-ring because my Vamo will only stay on while a battery is in it. It won't turn off at all now, so its pretty much useless. In other words, it may have had other issues besides the pin shorting. I tried to get the top off to work on it, but its in there too tight and I believe I'll destroy it if I keep trying.
Could this be a problem with the circuit board getting twisted so the buttons don't line up properly?