Nether Portal

This works correctly. The search range to connect portals is 128 blocks horizontally, going either to or from the nether. Since there is a 1/8 proportion between coordinates in the overworld and the nether, a link going into the nether won't always result in the portal leading back to the one entered, as it cannot find it. This results in a new portal created.

oh ok, so there's no way to fix this, maybe rebuilding the portal somewhere else will work?

That's right. IMO the easiest solution is to rebuild the portal in the nether closer to the overworld one.

This is really confusing me, because I've played for a year now in many different worlds/realms/servers, and never had this problem before.

BEFORE I would build a portal and light it, step in and go int the nether...when I stepped back into the portal I would then step out of the portal I created. They linked up together. Every time. Never did it create another portal in some random place. I would go in the nether portal in my portal room and step out of it in my Nether Base and vice versa....I built the first portal in our Realm last night and stepped through into the nether....Started building a nether base and mining quartz, then went back into the portal and ended up behind our house and a ways away. I broke the second portal, walked back and went through the first....went and in and out a few times and it didn't create another portal so I figure it was fixed.

Travelled 10k blocks away to my own personal base and built my portal there, went in and started tunneling towards our spawn base...when I went home it created a second portal and dumped me in an underwater cave. I broke that portal, went through mine again and then back, it created a third portal, floating above the ocean....broke THAT portal, went into the nether and back out again and it seemed ok, so I carried on about my work and play....when later I step out of tthe nether to go home and it creates a FOURTH portal and dumps me out....

Now, I understand how the game tries to find a portal...but I'm confused how it doesn't manage to find the portal I built, because it's obviously in range since it's usage is what caused the portal to BE created in the first place...Secondly, I've been in and out of a hundred portals and never had this happen before.

I agree with K. Nikki. I have had a home world since I've bought Minecraft and it has 5 portals in it, one at each corner and one almost the middle of my map. I've never had a problem until around the update that brought Amplified to X-Box 1 and PS-4. I figured that it should have been fixed by now. This is not normal operation. I play a PS-3 version, so it's not that I increased the size of the world.