The bug is about cheated heads (for example : /give "NAME" skull 1 3 {SkullOwner:MHF_Herobrine} ).when you have a head and you put it on your head,you don´t have a other face!
You can fix the bug,when you put the head on singleplayer gamemode on the ground and destroy the head.then you put it on your face you have another face!!!
duplicate of MC-51003 if you have not please use the search function in the future