Ask HN: Have you seen repeat/similiar submissions recently?

This is sort of a meta-question, which was prompted when I saw the another submission of the same url that I submitted reach the front page of HN. Is the HN submission tool broken?

My example: https://news.ycombinator.com/item?id=21918556 https://news.ycombinator.com/item?id=21913030

Example of similar posts: https://news.ycombinator.com/item?id=21918610 https://news.ycombinator.com/item?id=21916651

I'm sure there are other examples out there.