On my realm I have had three occasions in which a player has entered a nether portal and instead of being transported to the corresponding coordinates in the nether (if coming from the overworld) or in the overworld (if coming from the nether) they have instead found themselves in the exact same coordinates in the corresponding dimension. In other words it is as if the game forgets to divide by 8 or multiply by 8 for the position they are teleporting too .So far one player has had it happen twice in one portal coming from the overworld into the nether and another player has reported it happening to him once in a different portal coming from the nether into the overworld.