I encountered an issue when attempting to transport villagers through the nether to my base. I used a boat to bring the villager to the portal, upon breaking the boat both the villager and the boat item teleported into the nether. When I entered the nether, I picked up the boat entity however there was no villager to be seen. The only way to work around this was to have a friend load the portal in the nether, while I was sending through the villager. Without the nether loaded, it would have been impossible to transport the villagers through the nether. And a grueling process if I had to transport them in the overworld from (2077, x, -335) to (855, x, 62).

To recreate:

1: Use some desired method to cause a villager to collide with the nether portal.

2. Teleport through the nether and observe the absence of the villager.

To restate, the problem seems to be related with the nether portal not being loaded when a entity is sent through.