Put the summary of the bug you're having here

What I expected to happen was...:
I was taking my horse from a settlement far away from my home through a nether portal. I expected it to go through the Nether to the Overworld normally.

What actually happened was...:
The horse went into the Nether normally, but was unable to go through the other portal to the Overworld.

Steps to Reproduce:
1. Take a horse into the Nether.
2. Attempt to exit.