I've seen videos recently about newer patch notes and it sounded like mojang was trying to extend the world border, so I figured I'd report this problem because it might help. I've never seen anything like this before, every other block was gone. There was also a second layer at the bottom, it might've been the bedrock. I'm also sure it wasn't because I was stuck in a block, because I could move up and down and I could break the surrounding ice. Sorry I don't really know anything about the technical aspect of this, I just tried to get in a screen recording.