Wither Skull spawned without a direction "Flicker"

I'm trying to set up a GUI for Color Cube 2, And I'm Spawning slimes riding Wither Skulls with no direction, so that i can display their names without them being displayed. In the past when you gave a wither skull a tag of direction:[]
(Shouldn't direction be capitalized?) it would spawn a wither skull that you could not see, but if you gave it a name it would display that name. This is crucial in the making of this GUI, because No other entity can be invisible, and still display the name.

Another thing I noticed about the wither skulls is that even with an invisibility effect on, they still displayed their names, And still "flickered".
What I mean by that is that for brief moments you can see the wither skull.

To recreate this Just use the command;
Summon WitherSkull ~ ~ ~ {direction:[],CustomName:"HipsterSwag",CustomNameVisible:1}

Adding the invisibility effect doesn't stop the flicker either.