- build a nether portal and get a tamed sitting cat/dog
- push the cat/dog in the nether portal, so it goes to another dimension
- go in the nether portal
- click on the cat/dog, to let it stop sitting
- You will see that only the nether portal block is selected, and not the cat/dog. You only can let the cat stop sitting by destroying the nether portal.
This bug also happens when the cat/dog is sitting in tall grass or flowers