Thanks for the reply ,but the spacing distance isn't my problem since I'm not creating a new portal. this is the very first portal on this new server. I placed it on the surface and lit the portal,the game spawned the matching portal in the nether and i have not made any other portals on the server. the trouble comes on the 3rd or 4th time i return through the original portal in the nether to go to the surface. instead of returning to the original portal i started at, a new portal spawns on the surface about 180m from the original surface portal.
i have a vanilla un-moded minecraft server my brother and i have played on for about a year and we have 7 or 8 portals spread around the world with no issues so i have some experience placing them , i'm just not sure why it would randomly try to spawn a new surface portal on my return trip when it's all ready connected to one.