Hi,
I've been away form the game for a while so I didn't get to test this again until recently, but it is still an issue on 1.16.201.
As further info to this, it only seems to happen with the character creator skins. A player with the old-style skin doesn't cause the same issue.
I had this happento me today too. Was your original portal down below y=0? This is probably the same issue as MC-244742 on Java.
For reference, my original portal was at (129, -54, 9), which linked to (8, 73, 14) in the nether, but when I came back, a new portal was created at (65, -16, 124)