Blocks on mob heads not working

When mobs are spawned in with blocks on their heads via /summon, the blocks are enlarged

I summoned a Skeleton with a stained glass head and the block was huge, so I tried some others and they all didn't work.
A skeleton with a fitted "space helmet" looking head

I got the latest snapshot, and I summoned it and it didn't work

I used this command to summon it, sorry if it's a little fast.
/summon Skeleton ~ ~1 ~ {HealthF:60,CustomName:"Runner Skeleton",CustomNameVisible:1,Attributes:[{Name:generic.movementSpeed,Base:1.4},{Name:generic.maxHealth,Base:60},{Name:generic.knockbackResistance,Base:-1.0}],Equipment:[{id:261},{id:317},{},{},{id:95,Damage:0}]}
1. Put a step by step guide on how to trigger the bug here
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