Was trying to find some Event items to add to a trade.
The Brilliant Deer, So Much Floof, Holiday Cookie are in the Sets Tab.

I also found these other errors:
Unique Animal Hats is in Accessories Tab.
These are all listed in the Sets Tab and should be elsewhere:
1.5M (Imish Delight), 2M (The Herald), Another Orbit, Bountiful Cornucopia should be in Misc with the other Milestones and the common Basic Platform should be there instead of in Sets.
Unique Posh Hair should be in Orb tab.

Good to hear!

There's also an error when I try to open the Loopy Earrings. It doesn't show any of the colors I own (which should be all of them). It's just an empty box.