I need some help with nether portals. I currently have 3 portals that work fine. An overworld portal, a nether portal that is block away from the exact translated overworld coords, and an upper nether portal, 3 blocks from the exact translated overworld coords.

I am trying to move the nether portal. According the mine craft wiki I should be able to do this up to 128 blocks. But it is not working for me. I first constructed a new nether portal 50m from the existing one, and it created a new overworld portal. So I tried again from 40m, 30m and now 25m. Same every time a new overworld portal.

The upper nether portal is 3m off the coords and works. So how close do I have to get? Why can I not build a nether portal 50m from the overworld coords?

I have read a lot on this but it always assumes 2 overworld portals to one nether. I am trying the other way, I want several nether portals linking to one overworld and I want to know how far away I can move them in the nether?

Thanks in advance. Just spent an hour playing with this and still not closer to a solution.