The Bug

Players cannot exit the End dimension through the exit portal if they are riding an entity such as a boat or a horse, and have not viewed the credits yet.

If the player dismounts, they can go through the portal, however, the entity cannot for some time (even after the cooldown ends, they cannot go through the portal unless they exit and enter it again).

Steps to Reproduce

1. Create a new world to ensure the player has not seen the credits.
2. Run this command to teleport to the End:

   /execute in minecraft:the_end run tp @s 10 70 10

3. Kill the Ender Dragon using:

   /kill @n[type=minecraft:ender_dragon]

4. Summon an entity such as a boat or a tamed horse, and ride it into the End Portal.

Observed Results

The player does not travel through the portal, unless they dismount the entity. The entity also cannot travel through the exit portal, unless they exit and enter it again.

To view the latter part, teleport to the End using the command in the 2nd step.

Expected Results

The player-ridden entity should be able to travel through the portal, even if the credits have not been viewed.

Additional Notes

Discovered while testing MC-275550.

Relates to MC-272603, and is possibly caused by the fix of said issue.