When player in survival stands inside a nether portal, then clicks a bed to enter it (but has not exited the portal), a few seconds later the player is teleported to the nether at the mirror overworld coordinates (for example, if you are at 5000, 69, 5000 in the overworld, you will be teleported to the coordinated 5000, 69, 5000 in the nether), and sometimes a new portal will be generated.

I am unable to show this issue very well, except for a screenshot I took after the bug affected me. Extensive testing in a creative world later demonstrated this bug to be reproducable and consistent.

EDIT: As requested, I have managed to upload a clip of this bug, however it had to be split into 2 parts to avoid exceeding the file size