Joined entities such as spider jockeys and players riding in minecarts cannot transverse portals.
(dont know if actual bug) Minecart with player bug
Horses - Killed With Nether Portal
Cannot ride a horse through nether portal
cannot enter the nether while riding a horse
Mounted Horse by the Player
Horses won't use an Nether portal when riding it.
[Bug?] Mounted horses are unable to go through Nether portals
unable to ride into a netherportal with a minecart
Minecart cant travel in portal?
Horse through portal
While riding the horse you can not enter the ender portal.
You cannot ride a horse into the end.
Horses won't go into the END.
you can't ride on a horse into the nether (portal)
Horses causing bad game states when going through an End Portal
horse trough nether portal
cannot enter nether while in a minecart
Entities in mine carts cannot go through portals.
Cannot travel though nether portals while riding a skeleton horse
Players cannot go through nether portal whilst in Minecart or Boat.
Can't ride mobs thru portals
Players in boats cannot enter/leave netherworld through portal
Pigman chicken jockey won't go through the Nether Portal
zombie pigman chicken jockey won't go through nether portal
Can't use nether portals while riding a pig
Villagers in minecarts cannot move through portal
Can't Ride Through Nether Portals
Villiger in Minecart will not go into the portal
End gateways are no longer able to teleport boats with players riding in them