Astras cancelling themselves out.

[Eerol Kross]

Yah, so I just bought the Astra Flapping Black Devil Wings, to see if I liked how it went with my avy, and when I saved the changes both my wings and tail, which still showed up in the items listed for what I had equipped, didn't show up on my avy. I tried redoing this several times and the results are the same. Neither in the preview before I bought the item, or in my changing room when I equipped the wings was there a problem. It only occurs once I save the avy.

[Lady Saxophone]

Eerol Kross

Unfortunately the limit of animated items you can equip on your avatar is two.
This is due to the fact that animated items can only occupy two layers in the animated state - the far front or far back.
If you try to wear anymore than that, they will bump each other and disappear, as you have noticed.