First of all, hi and thank you for this nice mod.
Going straight to the point, as the title sais, I got invisible mannequins (and of course items they wear) as I put on them non-vanilla stuff. Some of them, instead, appear like usual vanilla armor set, for example leather armor, as they are a mod of the in-game armor.
I have a bunch of modded armor, too much to carry, and I like to put my stuff in display and order, so I really loved to see there is so much mannequins in your Armory. Sadly, this issue came up. I think that is not you to "blame" for that, but instead armor's modder, but maybe, being you a modder of course, I will get an answer as well :)