This happened to four of my tamed animals.
I'm on bedrock. My world was generated in 17.2. I'm playing in Realms and the bug appeared in 1.19.20.
Two horses were created as back-ups for our current mounts in case they died. They were teleported back to base, which is thousands of blocks away from the fence post they were leashed to. The fence post then broken. Once they were at the base we discovered they could not be leashed again.
Another horse, Cinder, was leashed to a fence post before this happened. Cinder was not initially teleported, but was ridden away from the fence post that was broken afterwards and the leash did not break. A leash knot was seen dangling from Cinder after the fence was broken. Because it was no longer possible to leash Cinder, he was also teleported thousands of blocks back to home base. Once at home base his leash was no longer visible. After this I would learn the command to kill leash knots, but it was not effective on invisible leash knots.
A third convirmed victim of a soft lock was a parrot. I don't remember leashing him or how he was separated from it, unfortunately. He was lost for several in-real-life days. After we located him it was discovered he too was soft locked.
I found a nft data editing tool and was able to drill down into each of their data packs. I found the Leasher ID for animals known to be both currently leash free and not soft locked, which is - 1, and reset the Leasher ID of the four soft locked animals to -1. This solved the problem.
How to recreate the error: open a minecraft world, preferably with a base of 17.10 or 17.20, apply all updates through 1.19.20. Tame an animal, leash it to a fence, teleport them thousands of blocks away while wearing the knot, and then break the fence post.
The expected result is that the leash knot breaks when stretched over a distance of thousands of blocks and the Leasher ID is reset to -1 (When I teleported with a different parrot on my shoulder this did happen.)
The actual result is that the leash knot is no longer visible but the animal retains the ID if the last leasher, rendering it unable to be leashed. This problem can also be captured when the wandering trader despawns while still attached to his llama(s). After he despawns the surviving llamas will also be soft locked.
On realms 1.19, using Android, y inversion is not currently working when the player is in a boat.
I've attached a screen recording. It looks like this is only happening with some words, but not all
This has been happening to my sister and I since 1.20.40. She plays on iOS (iPhone) with the latest updates. I play on Android 13. The world we play on is on Realms.