I play in a Minecraft Realms server with some friends. I play in my iOS, they play in W10. When I access an overworld nether portal it links with an existing nether portal and it doesn't generate the one it's supposed to. Then, if I try to access that same nether portal it won't take me back in the overworld nether portal I access, but to the original nether portal linked to the one in the nether. Both overworld portals are very far away from each other (800 blocks or so).