Another serious bug? Hoffmen keeps disappearing

[bi204-1]

I'm guess this must be a bug, but the Hoffmen character that you're supposed to be able to buy stuff from keeps disappearing in between waves, and doesn't come back. How am I supposed to be able to get more guns when he isn't around, and he is usually the only source for weapons in the game? Hopefully the devoloper will fix this in the next patch as well.