This is hard to replicate but bear with me - multiple people have experienced this
When in the nether or end, you will occasionally be teleported to the "overworld" against your will
However despite the fact that the sky appears as if it's the overworld, your coordinates have not changed, no blocks will display, and all models and mobs will still interract with you (including trying to kill you)
To replicate - just hang out in any other dimension while fixing bugs for 20 mins and you will see this happen
I fall under my portal that is in the nether after arriving and fall through the floor and then tp to, um, a random location that is the same everythime? Can I upload video?
A video would be best. Are you confirming the image above displays the same issue as this bug report?
Going to lock this thread for now as I really do think this is connected to the other glitch, so I will leave it like this to keep discussion regarding the bug within the one thread for simplicity. I'll reopen this thread if we find it to not be releated.