I have many instances of the same problem

We use a third party to bring in SCORM courses into Totara 12. Some users, even after completing the course, do not show completed in Totara.  For most they complete, but for some the completion record fails to update, preventing them from advancing in the training program. I end up having to manually complete these users to get them moved along, but why does the course complete for most, but not some? 

I'm pulling my hair trying to figure out what is going wrong. Is there something in course settings that could possibly prevent course completing?  

We typically set up training programs for our employees.  They have to complete a course list in order before moving onto the next round of courses.  

Any suggestions on what could be going wrong?  

We have all the typical suggestion in place i.e. 

• Open SCORM package in a separate window

Are there other best practices to help with this?