Research Article Submission
You should note that "Required Reviews Completed" status does not entail that "all" reviews are completed. It just suggests that a "minimal" set of reviews have come in.

For example, for few journals, the required number of reviews to make a decision could be 2; but, sometimes the editor sends an article to more than 2 reviewers. In that case, if he is not satisfied with the received reviews (i.e. at least two), then he waits for the few more.

In my recent paper, the status remained as it is for 2.5 months. Then, I reminded the journal EIC to expedite the process. Still, I had to wait for a month to receive the final decision.