whenever i partially destroy a portal in the nether (the 4 floor obsidian blocks are left), then die and reenter the overworld portal, there's a chance the nether portal won't respawn, and i'll end up standing on those 4 obsidian blocks with no portal behind/around me instead.
destroying those blocks will respawn the portal next time, but as long as they're there the portal has around 50% chance of getting respawned.
it's like minecraft still treats those few remaining blocks as a working, active portal.
edit: this actually happens as long as there's even one obsidian block remaining, even the top ones.
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I can also confirm this. Possibly related, immediately after this happened portals began changing destination with no discernible pattern. I had two fairly close together, and two also fairly close in the nether but at different height levels. They have worked before, but now it changes between defaulting to the top portal, and the bottom one. Both portals in one world will go to the same portal in the other, but will occasionally swap which portal that is. Very strange behavior.

Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.
Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been deliviered.
No response for over a year.
Confirmed.
I don't even get a new portal, if I destroy all blocks of the existing one.