Audience Split not working.. any advice?

Hello,

I decided to integrate the "Audience Split" step with hopes that I could separate two audiences in one campaign; with the first audience getting emails at 8am and the other at 5pm. Please see the image below for the framework of my campaign.

The problem here is that my team got BOTH of the emails on the 8AM send side. Its as if the "Opened Email Yes/No" step got confused. Why is this? If my team opened the first email, they should have been sent right to the "Wait" step at the end, but instead they got the second email...