Animals causing nether portals to glitch?

This is actually affecting version 1.20.1 on Java edition. Basically, nether portals are not working properly. In attempting to go through a nether portal from the nether roof to the overworld on an already predetermined portal, a new portal will be spawned about 50-100 blocks away from the current portal. I honestly have no explanation as to why this could be happening, but it is very frustrating. I am attaching a video of this happening. My only explanation could be that there is a bug with animals leaving the nether and it is messing up the portals as a result. I've noticed my animals will not travel through portals, essentially being trapped in the nether.

The file is too big so here is a link to YouTube where you can see this happening, as well as some screenshots.

https://youtu.be/jaNLkVPdG60