Let me say first that I have 100% working, stationary mannequins. They don't shift poses/positions when I enter the house and they display armor properly, you'd never know something was amiss until the invisible NPC bumps into you, knocks a neatly stacked pile of ingots over, kicks a basket, etc.

I have triple checked to make sure that the Xmarker and Mannequin are properly linked to each other, the mannequin's parent is set to the trigger and player enabled and the xtrigger primitive is checked. All x/y positions of the three are matched so they stack perfectly onto each other.

The only other wierd thing I noticed is that none of my mannequins have collision unlike the Vanilla ones. I've tried comparing mine to the one in Vlindril Hall and can't find any difference.

Any advice?

I have this problem with some mannequins I was just using with markers for scenery.

It seems to only happen in certain parts of the room, and the wiki says something about
position being an unknown problem.