Current skinCache in TileEntitySkull has small issue. It searches skin for skull and writes it in cache with pair of name-gameprofile.

Issue is really small. It searches in cache with normal nick name, and if skin not found, it lookups for the skin and writes it with lower cased name!

To fix skin cache you need:

1. Go to TileEntitiSkull
2. Search for method ` public static void b(final GameProfile gameprofile, final Predicate<GameProfile> callback) { `
3. Find line with `final GameProfile profile = skinCache.getUnchecked(gameprofile.getName().toLowerCase());`
4. Change this line to `final GameProfile profile = skinCache.getUnchecked(gameprofile.getName());`

And skin cache will be fixed! No more workarounds for heads!

p.s. version copied from another issue. I don't see fix here:

https://hub.spigotmc.org/stash/projects/SPIGOT/repos/spigot/browse/CraftBukkit-Patches/0092-Convert-player-skulls-async.patch

So, i reported about this. Sorry for bad english.