I created a nether portal at x200, y63, z1600 in the overworld on a cobblestone platform next to an iceberg

i then created a corresponding portal in the nether at x25, y99, z200 

however whenever i go I go through the nether portal it creates a new portal at x161, y100, z1202 in the middle of the air above the ocean

if I delete this portal and enter the nether through the original portal and then go back to the overworld, it recreates the portal.

the original portal links back to the nether but the nether never links to the portal despite the coordinates being exactly divisible by 8

i tried lowering the portal in the nether to y63 but the same issue still occurs