Mcpe-115933 slightly touches on the issue. They dont stay linked to the same portals for long and the cords have no logical rhyme or reason to them other than just random. My game has made so many nether portals at so many completely random xyz cords off the same overworld portal i cant even keep track. Some of which going through the same overworld portal will never send you back to, so i cant even re-find them to get the cords.
One overworld portal we used continuously for months used to at least send us to one of two semi-close nether portals at random, until it suddenly decided to start spawning us inside walls at random locations. I can walk through a portal we've used 100's of times, then my friend a moment later and both end up in different places in the nether far away from each other next to two newly created nether portals, while the original ones it used to link to are still standing, lit and protected inside bases. Or either just kills us while we are on a "building world" screen before we've even loaded in losing all our items we spent days and weeks working to collect.
Honestly, since we've quit playing out of sheer frustration its not really worth more headache to try going through the portal dozens of times just hoping it actually spawns me in the same spot twice, or even spawns me in the nether at all without just killing me, to get cords on it.
you dont need portal coordinates to tell that maybe someone should be playtesting these updates before they are released an make the game unplayable.