Firebug grenade glitch

[SUPERTIME]

So I encountered a bug last night. It doesn't happen every time, but maybe 40% of the time when I threw a grenade as Firebug then lit it on fire with the flamethrower to make it explode faster, it would expend ALL of my tank without even shooting fire. I had to switch weapons to make it stop, not even clicking would make it stop until it had used up the entire tank. Very annoying since I had to be watching my ammo rather than the zombies.

Has this happened to anyone else?