So I was editing This Question and what I was doing was very simple. I was moving the problem description before the code.
I tried to submit the edit, but it told me that
A question with that title already exists
The following posts seem to suggest that we use to have this issue, but it has since been fixed.
But apparently the bug is back.
PS, I know that I could change the title, but the bug still exists. the user was still able to submit a question with that title.