Your claim can always be pushed back in the process up until it reaches "Preparation for Notification". I don't know anyone personally that doesn't have the "requested evidence is past due" part. Don't know what the deal is with it, but rest assured, you can and will receive at least preliminary ratings even with that note on there. Don't expect to receive preliminary ratings until it does reach the "Pending Decision Approval" and stays there for a few days (depending on how active they are at updating the site at the time). If you are still active duty, it will sit in that state until you actually EAS, at which point they will move to finalize the ratings, or...yes, send it back (even as far back as "Gathering of Evidence". I have only heard of 1 person that this happened to, but it has, and can happen. For most, it just gets finalized within 30 days after your EAS and you will start getting your $$ on time, as expected.
In your circumstance, it sounds like the final authority on preliminary ratings disagreed with the VA Rep who sent it, so wanted more justification on why it was as high/low as it was. Could be a new person in either spot. Could be that someone copied and pasted the wrong thing and just has to correct that. I wouldn't worry too much on it. Review of Evidence is one of the faster stages, so feel blessed it only went back to that spot!
Hope this helps (and eases your mind)!