Put the summary of the bug you're having here

What I expected to happen was...:
When returning from the nether i expected to return in the same nether portal I used to get to the nether

What actually happened was...:
A new nether portal was unnecessarily created in the overworld even though nothing had happened to the initial nether portal

Steps to Reproduce:
I am unsure as to if this is just a bug caused by the location of my nether portal but this is where they are placed. The initial nether portal (a 3x3 portal, 5x5 obsidian ring) is located at coordinates (1272,11,-230). It transports me to the nether where the nether portal is then located at (143,101,-46) within the nether, but when going through the portal in the nether it transports me to a game generated portal at (1142,72,-300) that didnt exist before coming back from the nether the first time. this new portal brings me back to the original portal within the nether but the portal within the nether will never bring me to my initially created portal.