Teleporting seems to occur when near a corner in a room and commonly when beds are situated in a corner. Building furniture near a wall corner (even on the outside) can cause teleporting to another room or outside.
The teleporting inside probably happens with all furniture - its just that clothes stands tend to be the one of the few items that get built in numbers along with chairs/stools.
That and the fact that I always use the instant moving Mod means that I build them in a bunch.
Though it has happened numerous times when near corners when building in furniture close to walls, T-intersections and corners 
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Edit: Even happens when building fence railings near the top of staircases - though not all the time.
Thanks a lot @roo! I’ve saved this thread for when I get to investigating it.
If anyone else sees this and has other methods to teleport villagers reliably, feel free to post them here, too!
Had a few teleportations over the last few weeks and they all occurred when starting a saved game from the previous day.
There are no stairs built yet for this house, so had to build them to get him down 
I started the game save and the 3 Foundies were originally building the top floor from below (image 2)
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But they appeared back down on the ground floor (image 3) when the game started in the exact positions they should have been up 1 level in image 2.
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I don’t think the getting food through the window is a problem but just thought to add it to this list while I was posting others
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Been noticing a few small glitches in the game recently -
so started a new game yesterday - vanilla, no mod’s
A minor problem, one Goblin village all have completely white heads.
Today a auto teleport at the beginning of game again - image 2
The 3rd image you can see the haze of a game starting and before pausing the game you could see the Foundy on the ground floor for a micro-second before teleport.
Will see how it goes, but may look at a game re-install tomorrow as there have been a number of odd glitches and not sure what the problem is.
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I see. Sorry for the late answer.
Do you still have the saves for these?
Especially the one where the Foundy starts out on ground level and then teleports up when starting.
You probably already know, but send them to daniel@dionicsoftware.com 
Thanks!
Oh and I know about eating through the windows. In my opinion it looks fun and makes some sense - it’s just that the window doesn’t open when they do it.
