I'm not sure if this is intended but the only way I can get it to reliably change skins is if I restart the client

I have recently been looking into the code and trying to find a fix but I will likely just open a minecraft bug report because it is an issue with the game and not my mod. The same behavior happens with changing from minecraft.net

Thank you for investigating this. I will try to get it fixed in the next version.

bump for potential fix found