Ok so I purchase my property in Riften and go to check it out. I read that there were mannequins so I went directly to the basemant to store some armor on them. Much to my surprise, the mannequins ARE MOVING. Not walking around but the heads looking at me and their bodies swaying back and forth like NPCs do. Also, Anytime I try to hang a weapon in that house they glitch into the wall. I really hope the patch coming fixes this...

Oh and none of the bookshelves work. Wtf?? Bethesda dropped the ball on this house.

My mannequins would move in that house too. Sometimes they would be off there standing area but if you want to click on them you still would click on where they are supposed to be. Also I loaded a save inside the house and everything was gone (all the upgrades). Just exit the house and renter that's what I did and it seemed to work. Also you could just load the auto save from when you enter and it should be fine.
Hopefully it works, good luck.

Also it seems that if you purchase the home and all the furnishings at the same time, before you even exit the conversation. You will be less likely to experience these issues. I know it seemed to work for me, mannequins still move occasionally if I reload a save in the house. Even had one of the mannequins appear with its head stuck in the ceiling, for a second I thought someone hung themselves in my house!