Nether Portal Doesn't Work With Small World Border

Context: I’m making one of those maps where you start with a world border of 1 and it expands each time you get an achievement to play with a couple of my friends. I was going to do a nether section but the portals don’t seem to be working.

Information: It will spawn me at 0 0 in the nether and I can fly over to the world border from there in the nether. The portal was within the border but it put me over at 0 0, the bigger the world border the closer it brings me to where it should be taking me. It even happens when the world border size is the only thing I change and don’t touch the portals or terrain. I did some experimenting and if the world border is above ~375 then it usually works. I don’t know what the problem is. I am also around -1400 x and -500 z in the overworld if that has something to do with it. This is a single-player world and I was going to import it to my server when it was finished so it shouldn’t be some sort of server glitch.

Options & Restrictions: I don’t know if this is a bug and I can’t do anything about it, if it’s something client-side & I need to reset the world, or if there is some other solution I just can’t see. Also, I found an old bug that’s supposedly resolved: MC-53555, might be that the bug has come back but I don’t know how that works. I wanted to choose a nice spot for this map I’m making so I don’t want to move to 0 0 in the overworld. Obviously, I am open to using commands so if there are any command block solutions I’m all ears. Is there anything I can do?