When a ceiling crush a spawned creature it does not leave any corpse or guts. It just dissapears.

Does it happens in all the games or just one in specific??

Well, I didn't checked other games. It happens in my mod, which is based on Hexen progs. But I am absolutely sure that I haven't changed anything referring to creature's deaths.

I just tested it in Doom, and the same thing happens. As soon as the crusher touches the monster, Vavoom acts like it performs a "thing remove" action on it. This happens even if the crushers damage is set to 0. I also noticed that the "Vavoom_Doom2" config file for Doom Builder is missing both MapSpot and MapSpot(gravity) things. Not sure about the others though.

Doesn't happen in current version.