End gateway teleportation fails when player is passenger of boat or horse

When a player tries to travel through an end gateway while riding a boat, one of the following bugs can happen for gateways generated in the end:

• Player and boat are teleported, chunks are not loading and constant server warning "Boat (vehicle of [Player]) moved too quickly!"
• Only boat is teleported, chunks unload for player and once server warning

And this happens when creating a custom end gateway:

• Yellow beam appears and client renders about every second teleportation but boat and player stay at their position

How to reproduce

1. Kill the EnderDragon
2. Try to travel through the portal in a boat

Note: This works fine for Minecarts