Custom Player Heads Bug

So this is a glitch with Custom Player Heads in Minecraft.

I used both of the commands correctly for "MHC_Villager" 's head but the head kept turning from Steve to Alex. I tried some other player heads, and same thing. I saw a forum post and it was "Essentials" overriding the command, but I don't know what that is. So I hope this bug is fixed or at least I get some instructions to fix this. I don't know if it's a Client, Internet, or Version problem so please help.

• Thanks.