This might be a known problem (or possibly not a bug, I don't know), and if it is, I apologise. Anyway, there is this possible bug on my vanilla multiplayer server (and other multiplayer options) where when you make a Nether portal (besides the first Portal made) you have to go to the exact coordinates in the Nether and make a new one to link it, otherwise when you go through, it comes out of a random portal in the Nether. It's really time consuming and frustrating, is this a bug? Or is this a feature?