Nether portals not syncing properly

my nether portals wont sync to the correct portal in the alternate dimension. from what i can see from testing in a few different creative worlds is that all portals in the nether are syncing up with the most recently created portal in the overworld. unless they are separated by a few hundred blocks in the nether.
i had superflat saved from when i was learning how to sync portals and all those portals are now desynced and are doing the same thing as my new worlds.