Nether Portal at incorrect location

My world seed is -2991310406697944721. I created my first portal from the overworld to the nether at coords -77, 10, -40/-41. When I went through it I came out in the nether at -26, 45, 9/10. When I went back through the same portal from the nether to the overworld, instead of going through the portal I came out of a new portal created by the game at -197, 26, 76/77. even though my orignial portal was still intact.

What I expected to happen was...:
I expected to come through my portal in the overworld at -77, 10, -40/-41.

What actually happened was...:
The game created a new portal in the overworld at -197, 26, 76/77 and I came out there.

Steps to Reproduce:

1. Create a new game with world seed -2991310406697944721.
2. Create a nether portal at coords -77, 10, -40/-41.
3. Walk through the portal.
4. Turn around and go through the portal from the nether to the overworld.