Ender Dragon spawned in Overworld travels to 0,0,0

All Ender Dragons spawned (by /summon EnderDragon ~ ~ ~

{DragonPhase:0}

and other methods) travel to, and stay at the coordinates of 0, 0, 0. This is especially an issue when spawned in the Overworld.

I've looked at previous tickets on the issue which seem to suggest spawning the dragon via the above command somehow corrects the issue - it does not.