The Sclerite Karka Shell back skin disappears when you use an emote, but also on random moments, and I couldn’t find out yet what moments these exactly are. Anyway, the skin disappears and I have to make it unvisible and then visible to let it appear again. I’m not sure if this issue is skin related, or item related, because I use the upgraded, Ascended version of it.
Riselight [WvW] – Elementalist
Smough The Cruel [WvW] – Warrior