Learners Not Able to Move Beyond Quiz

Hello,

I've been building out courses for staff with the same settings for months, which includes having two branches to match the two positions in our stores. The format has always been:

Overview → Choose either path 1, 2, or QRG → Path 1 or 2, depending on role → A QRG page with content for both roles → The quiz → A resources & exit page. Navigation has always been turned off for these courses so that staff have to view at least the overview and refresher page before advancing to the quiz. 

This format has been working without any issues for the past year (about 10 courses), but for some reason, this most recent course doesn't allow anyone to advance beyond the quiz. I have it set to track quiz results instead of course completion, so why are learners being stopped, and how do I fix it without opening course navigation?