Hostile mob doesn't teleport correctly when overworld/nether is already loaded

So i was building a Ghast farm and i found that out that Hostile mobs doesn't teleport correctly to the overworld (sometime even from the overworld to the nether)

*No specific map is needed (tested in many worlds)
*No special gamemode is needed
*Day/Night doesn't affect
*Tested on more than just Ghast & Pigman ( Zombie ) (I already lost my horse in the past cause of that) So i think it's not just affecting hostile mobs
*If the portal in the nether is from the first natural generation, the mobs might be able to teleport to the overworld correctly (tested)
*Pushing them or letting them going by them self in the portal doesn't change anything.
*Test on Single Player world
*I Tested on a vanilla Multiplayer server. Same thing happen.
Here is what is going on:
https://www.youtube.com/watch?v=xnvhqFdIxbk

Note: (not showed in the video) ;
Out of scene i saw them in the overworld (when i tried other time before recording) and they was just dispawning in my face [Next to me, they was like 5blocks far of me...].
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News for this issue (I just guess this may be the cause):
https://youtu.be/L59BK6ieJxM
*You clearly see him a short time before it dispawn.
I think when the overworld is already loaded and mobs go to it will do a bug and make them dispawn.
Example:
I'm in the overworld, a friend in the nether, the mobs is pushed by him/me to the overworld/nether and it will bug-dispawn.