Mobs moving from Nether to Overworld through portals Disappear

Context:

Currently I am playing in a Java realm on MacOS with some friends, I am attempting to complete a few advanced achievements such as killing all mobs (with the Zoglin being the only mob left) and an uneasy alliance (bringing a Ghast from the Nether to the Overworld to kill it).

 

Problem:

However both of these have been a much greater challenge than initially anticipated, as with both, the mob I am trying to transport simply disappears the instant they enter a portal in the Nether, and to not show up on the Overworld side.

This is the case- no matter the size of both portals, and regardless of if either side is loaded. (I've tried having a player on each side.)

I understand that Hoglins fear portal blocks, but on a single player world this is easily combatted via use of a lead. However in the realm no matter whether I use a lead, a boat or a fishing rod, the mob simply does not show up on the Overworld side.

The third instance in which this has happened was a lot simpler, no leads, no fishing rods, no crazy sized portals.

Simply bringing an Silverfish from the stronghold across the roof of the nether, and through my main base's portal, again, walks through the Nether portal- no worries. However is no where to be seen on the Overworld side.

 

Tried and failed solutions:

• Making both portals significantly bigger.
• Keeping each side loaded.
• Playing with or without Optifine (as there was the possibility they were simply invisible.)
• Any order of me first or the mob first.
• Relogging, and restarting both the client and the realm.

 

 

Any help would be greatly appreciated. 

Cheers!