Issues with Oracle not marking learning complete

Sounds to me like the LMS isn't getting the completion data from the user, and that's often caused by a poor internet connection. This can also happen if users take the course during times of high internet usage at their location; I've seen people unable to complete a course at 9 AM, but could complete it at 12:30 (when most of the building went to lunch). Also, extensions can be to blame, as well as folks with their pop-up blocker turned on. 

When I dealt with this, I'd suggest them taking it at slower times, make sure that they didn't have any extensions that would get in the way, and then if all that failed, force-complete the course for them in the LMS. You really get into diminishing returns if they've tried to take the course more than 3 times.