Alrighty, did some more testing and I'll put as much info here as I can so maybe you can come up with something. On my alt, that has never had a head drop before I was using Skin A, I got a head which we will call Head 1. Head 1 worked fine for a day or two, but then I changed my skin to Skin B, because I wanted a new display head. I was able to wear this skin around for a good while and Head 1 didn't change, it remained as Skin A. However, once I got Head 2, using Skin B and returned, Head 1 was now using Skin B, both heads were. Logging out, changing servers, leaving the area and even sometimes just turning away and looking back both Head 1 and Head 2 will choose a random skin now, but are always in sync. Even further testing; If you get Head 1 using Skin A on say SMP1, then go to SMP2 with Skin B to get Head 2, as long as Head 1 never goes to SMP2, and Head 2 never goes to SMP1, those heads will always be the correct skin. Once a new head using a new skin of a single player is introduced into a single SMP that head becomes randomized for all the head skins the SMP has previously seen. Hopefully this info helps in some way. Edit: Forgot to mention, if you get 2 of Head 1, and 2 of Head 2, no amount of vaulting or anything will allow those heads to stack, the data is there that they are different, it's purely a cosmetic bug. I'm sure you knew this but figured I'd add it.
yea, my head since I changed my skin, changed to my NEW skin but sometimes when I log on its my old head
So I ended up with 17 new heads. They originally were the old skin when dropped. They were put in vault and then showed the new skin. However they do not stack with the other 40 I have, even after being in vault. And they change back again after server jumping with them in vault. I have them in my 2nd vault if it helps you to look at them.
At this point it seems like its purely mojang client bug not handling different skins for same user at the same time and i wont be able to do anything about it.
