Yeah, it's a known bug.
Tunneller has AI copied form Imp; this includes the smoking code - but there's no animation sequence for smoking tunnellers - which leads to "transformation".

This doesn't have anything to do with anything, but once, a while ago, I had tortured a tunneler until he was mine. Me and my brother watched the tunneler (they have a weird AI)for a while, and all of a sudden, it morphed into a HELLHOUND! Me and my brother were like "WTF?" and ten seconds after the "transformation",the game crashed. I just wanted to let you guys know about this, and I was wondering if it ever happened to you?
Yeah, it's a known bug.
Tunneller has AI copied form Imp; this includes the smoking code - but there's no animation sequence for smoking tunnellers - which leads to "transformation".
Ah, ok then, cheers. It's just that I looked it up on google and there was nio results, so I thought it was unique.

