Q: What does a status change from "Required reviews completed" back to "Under review" mean?

Detailed Question -

I submitted my paper to the journal Expert Systems With Applications. After a month, I received comments from three reviewers requesting minor revisions. I edited my manuscript as they suggested and submitted the revised version. After 3 weeks my paper status was changed to "Required reviews completed" but after a day it was changed to "Under review" again. Could you guide me what it means and is it possible the reviewers reject it despite their first opinions?

2 Answers to this question
Answer:

The status changing to "Under review" once again after "Required reviews completed" indicates that the editor has sent your paper for an additional review. this is quite a common scenario. If the reviews are weak or conflicting, and the editor feels that he/she is unable to take a decision on your paper based on the reviews, he/she can send it for an additional review.

Another possibility is that when the status first changed to "Required reviews completed" after resubmitting your paper, it was reviewed by the editor himself/herself. Often, in case of minor revisions, the editor himself/herself reviews the manuscript and does not send it back to the reviewers. But after going through it, the editor might have felt the need to run it by an external reviewer, which is why the status changed to "under review" once again. 

Related reading: 

Why has the status changed from "Reviews completed" to "Under review" and then to "Reviewers assigned"?

Answer: Dear Dr. Z, I have encountered the same case with you. How is the paper going, hope it has been accepted. FJ