My battle with doors continues as new bugs pop up. Made the doors in several varieties, put them in GECK, everything seems fine.
But in-game in the test cell some of the doors just don't show up at all - no collision, no model, no textures, nothing. That wouldn't be weird by itself except I have the same model under the same reference in another place and it works 100% fine.

doors in GECK:

ingame wtf:

You can see in the in-game screenshot there's supposed to be a door in the doorframe, but nothing's there. The same model/reference is on the right side of the screen working 100%. But the door with glass has disappeared too.

The fault can't be in the models, but I can't see anything wrong in GECK either. This is some straight up Twin Peaks stuff so, again, any help would be greatly appreciated.

EDIT: So after some tests it seems the fault may be in the models. I made a new test mod and added the doors and still some of them disappear in-game. So the problem might be with animated nifs? Are there some strings that are missing  that I should add?

EDIT EDIT: Solved it! Turns out the problem was simple and stupid as usual - the nifs had referenced a collision file in their root Node which made only one copy of a model working per game.

I'm an idiot:

It needed to be empty so now everything works. I hope my dumb mistakes will help someone else to avoid them in the future.