Peter, does your light have a big fat looking bulb or a very long and skinny looking bulb? I'm trying to figure out if yours has a stock or modified one.
In any case, if your light has a long, thin bulb it means that the outer bulb envelope has been removed in order to use a reflector with a smaller hole and in improve the beam. The only problem with that is that the bulb is more vulnerable to breakage because the thin glass structure is so fragile to something touching it. When the head is off the light it's susceptable to braking by very little force and when the head is on the bulb can be broken from screwing the head down too far causing the inside of the lens to make contact with the tip of the bulb.
Anyhow, I'm not sure if this is even relevant, but the thought occurred to me when you were seeing a blue arc and then got zapped.