This relates maybe to: MC-52653 and MC-65587
It seems like everytime you give yourselft a skull and the SkullOwner tag contains something with "MHF_" the game freezes (probably because of MC-65587), BUT also when placing it
How to reproduce
/give @p skull 1 3 {SkullOwner:MHF} mhf is a player, no lag while placing
/give @p skull 1 3 {SkullOwner:MHF_1} MHF_1 is a player, lag while placing
/give @p skull 1 3 {SkullOwner:MHF_2} MHF_2 is probably not a player, lag while placing
/give @p skull 1 3 {SkullOwner:MHF_sheep} MHF_sheep is added by MOJANG, no lag while placing
it seems like it freezes or lags not every time, sometimes it has only a delay
Linked issues
Comments
marcono1234
No, that is not what I am describing, like you see placing a head from any player whos name doesn't contain "mhf_" doesn't cause lag when placed on the ground!
The search really nailed it this time. I gave myself a Herobrine head and it froze temporarily the first time. Then I gave myself a killercreeper_55 head and it froze longer, but it still unfreezed.
marcono1234
What you are describing sounds more like MC-65587
marcono1234
Looks like "MHF_1" is not a player name. There is only delay when placing a head of a player which does not exist.
It takes time to find the right head in a database of more than 16 million players.