Do not store any dragon masks on the mannequins in the Manor. I placed all of mine on the various mannequins only to find them completely gone several hours later.

Literally every single Dragon Priest Mask in the game is now gone from a save 20 hours prior, including all the new masks with the exception of Miraak's.

I would love it if someone else can confirm this.

I don't have any problem with the mannequins...
Sorry for you..

There are 9 original dragon priest masks and 4 mannequins, I know there are a few new masks so how could you lose so many masks with so few mannequins? That wooden mask will vanish no matter what you do, it is only safe in storage. I only ever tested a few masks on mannequins and they were fine, but mannequins in Severin Manor should display armor and keep it exactly the same as the ones in the original houses we brought.

I will go grab all the original masks tomorrow and test it out. Personally I prefer my masks in a display case.

^this^
Good point, aussie. Quite possibly the culprit.
I've only ever stored the wooden one and displayed the others in cases.

I know that I've got buggy mannequins like the ones I've had in Hearthfire and Honeyside: replicates whatever armor you first put on it. I think I've got unlimited Dragonscale, Nightingale, Morag Tong, and blacksmith clothes now.

I wasn't displaying all the masks. I am something of a pack rat so I have a lot of different houses. I deliberately placed all the masks in the mannequins at the manor so I'd know that's where they are.

I didn't have the wooden mask yet, it was actually when I retrieved that mask that I discovered all the rest were missing. I went back to grab the masks to unlock the 9th but they were all gone.

Someone mentioned that mannequins are known to reset every now and then, but I have never encountered this bug in any house aside from Severin Manor. I actually stored the masks on my mannequins in Honeyside for about 100 hours without a problem. That's why I believe this to be a Manor specific problem.

Mannequins never reset, not even the Dawnguard Fort one will lose your stuff, but they are not meant for storing large amounts of items either, we have plenty of containers for that. Are you sure you did not move the masks some where else?

I am just off to fetch Braggen's collection and test the new mannequins out.

It hasn't duplicated or eaten anything for me. All it does is move the mannequins around the bedroom for me.

Annoying little wanderers.
There is a fix, though.
- Click where the mannequin is supposed to be; you'll get a cursor
- Remove an item and give it right back
- Exit the menu and the mannequin will snap back to it's pedestal

After doing this once, the mannequins should stay in place. At least they have for my characters. Your mileage may vary.
Hope that helps

Absolutely positive I did not. They were in Honeyside, then I moved them to the Manor. I didn't think that they reset, but someone mentioned it was a possibility. I distinctly remember placing them on the mannequins because I would remember that.

Well I tested mine out, nothing vanished and I now have 3 copies of one of the new masks. Each mannequin was tested with the 9 original and one newer one that I have, all worked fine. All four mannequins duplicate the new Armor I put on them, I smithed them all up to Legendary, it just remived the improvments and duplicated the sets. My mannequins also change poses which is nice, either that or they are trying to escape and being frozen in place. They never walked of the mats, but they sulked sometimes and took their time appearing.

I was testing to see if they dispose of extra items after the house resets, but as usual the game has stuffed up and frozen, this time just outside the Manor. It always seems to be a bit glitchy there, but it has bugged out good and proper this time and seems unlikley to recover. I never saved anything since nothing I am doing is staying in my game, my masks stay in their display case. If I have the patience I will go get the masks again, put them on the mannequins again, then wait ten days and this time save it before trying to get back in the house.

i have had duplicated armor on the mannequin on the left right in front of you as you enter the room. had a set of bonemold armor on it took it all away, left came back and it was all back on the mannequin repeated this a few times just to make sure i wasn't being a ditz