I've noticed that with the new question asking form, sometimes, attempting to submit a question will post two, or rarely more than two, identical copies of the same question with identical timestamps and sequential post IDs.
I've had this happen to me once before (double post), but at the time, I assumed it was just a temporary fluke. As far as I remember, I just reviewed the question, saw no errors, and submitted it. (That's all the info I have.)
However, I just saw this happen to someone else, so it can't just be a fluke on my end. This is the question they tried to post, and this is the double post. The author claims there that they did indeed double click the "Review" button, but their question didn't go through since it didn't have a required tag, but when they tried to submit the question with the required tag, they only clicked it once.
Also, now that I think about it, it could not have been just a temporary client-side issue on both our ends. The system is supposed to prompt for a CAPTCHA if one tries to post more than one question in 30 seconds. Neither of us got a CAPTCHA. This means that the server accepted the double post, and so it's a server issue.
This has the effect of denying users badges that they would have otherwise qualified for, since a single negatively-received, closed, or deleted question will make that day not count for the Curious, Inquisitive, and Socratic badges. This means that even if the double post is deleted and the original is upvoted, the user won't qualify for that day since they've made a "bad" question on that day. (While they may be able to later reverse this 60 days later by undeleting and re-deleting their question - questions deleted more than 60 days later aren't considered "deleted" for the check - they often won't be able to, since most of the time, users will have downvoted the double post, which also disqualifies one from the badges.)
Can an employee go through server logs to see what happened in both these cases, and add some safeguards to prevent accidental double submissions of questions? This seems to have come up when the new asking form was deployed.
This SEDE query, forked from a query rene wrote in the comments, lists instances of this bug. Note that it does have some false negatives (cases retained question's tags were later edited, as the only content that can be queried for in deleted posts is the tags), and it may also have false positives where two questions with the same tags happened to be posted at the same time by two different users, one of whom was later deleted or dissociated from the post.