Zandronum

Often, when a monster is teleporting, I see a single frame of the monster in mid-air, as if the monster is moving really fast to the teleport destination, rather than instantly teleporting. Do you guys ever see this? Is this a bug that I should report on the tracker?

Example WAD or demo/video?

I've never witnessed it but it sounds like clientside interpolation of the monster's position change.

I have monster interpolation enabled and I can't recall ever having seen something like that.

Actually yes. Although I see this with players being propelled extremely fast for a single tic. Doesn't bother me though, it's too rare to be worth a report.

I first noticed this when i teleported monsters into a sector with a height of about 1024 (sky as well).

I've seen it in several maps in different wads, but I made a simple test map, and it didn't happen, so I don't know exactly how to reproduce it.