Problem with Results of Results Screens

I'm experiencing some very erratic behavior on a Storyline course.

I've got about 100 people in the LMS (Cornerstone) who show Completed with a score of 100 (so I know it's working some of the time.) Meanwhile I'm also seeing about 150 people who show as "Incomplete" in the LMS with a score of 100 on the same course. (So I know it's NOT working some of the time.)

This course is MUCH longer than our usual courses (about 45+ min) and the final results screen is a "Result of Results Screens" and it combines 10 results screens. Previously, I've only used a single results screen which totals up the questions, and this is the first time I've used the rollup of several results screens.

What I'm noticing is that most of the people who have had the "Incomplete" with 100% score on the LMS are saying they exited and resumed at some point.  (some saying the started at work and finished at home)

Has anyone had a similar experience with this kind of erratic behavior with either:

1. Really long courses that people often exit and resume

2. Used a results screen of other results screens instead of just based on questions

3. A combination of 1 and 2?

I'm thinking it's happening too much for it to be just LMS timeout related.

Any suggestions?