Create new portal in the overworld. On the first-time teleport, I wind up in the Nether but not standing in a portal...falling from a great height resulting in crash and death.

After respawning, I go through the portal again and it now connects to a Nether portal, but all my stuff (lost when I died) is nowhere near the portal.

The first time I teleport back to the overworld through this portal, the same thing happens...I appear in space without a portal and crash to the ground.

After respawning, I go through the portal to the Nether successfully. Then go back through the Nether portal, and this time I come out an overworld portal that was spontaneously created some distance (100 to 200 blocks) away from my original overworld portal.

I destroy this new portal and repeat the cycle. Another new portal is created in the approximate location of the portal I destroyed.

The behavior is very repeatable, and very wrong.