When you break a door at the bottom of it, it shows like a half door for a very brief moment then it disappears. However, when you break the door on it's top part, it breaks like normal. Surprisingly, this effects 1.8 as well.

Note: before watching the video, I would suggest to make the video play slower so you can see the bug occurring as it happens really fast that may make it hard to notice when played the video in a normal speed. I suggest putting the speed at 0.5.

Video evidence: https://youtu.be/nJPeBL8WYYE