Q: Is it a bad sign if the status changes from Decision Pending to Out for Review the same day?

Not necessarily. It looks like the Associate/Managing Editor (AE/ME) reached a decision on your paper after the first review, but that decision was changed/rescinded by the Editor-in-Chief (EIC). The EIC (or even both, after a consultation) may have decided that your paper needs an additional review for some reason. (Perhaps your paper is in a new or niche area?) There is nothing much to be worried about for now. In fact, your paper being sent for a second review means that the editors want to make sure they are vetting the science for accuracy and quality, which can only be good for everyone: the journal, its readers, and even you [though yes, if the next decision is a major review, it may mean some (re)work]. Also, we think that the journal seems to be making fairly timely decisions, at least based on the statuses you have provided, rather than holding it up. That’s another good sign.

So, presently, you should simply wait for the next round of review to be over. For insights into peer review and journal decision-making that may help address any remaining worries, you may wish to go through the following articles:

• Peer review process and editorial decision making at journals
• How a journal editor reaches a decision on a manuscript after peer review

Hope that helps. All the best for the next update!