What did they use to build the SCORM? Can you access information in the source file about what variables it uses and how it uses them? I use Lectora and (of course) Moodle...but I collaborate with a few people who use different LMS...when we share source files, we each have to check completion status options to make sure they report properly...We almost always use AICC_Lesson_Status in Lectora to indicate completion...mine has to be set to "completed" (all lower case) while one of my collegues has to set it to "complete" and yet another has to use "Completed"--it might be as simple as that.
In the Moodle SCORM activity settings for attempts management I usually use unlimited attempts (though...sometimes that's not a great plan), I don't force a new attempt (though if you don't like doing the start where I left off bit, you might want to do that...I just don't like making people start over if they didn't finish in one sitting) and I don't lock it.
Compatibility settings all get set to NO (but I'm rethinking this).
In Activity Completion, I set it to complete when conditions are met and I set a required passing score (all of my modules give 100 upon completion, regardless of grade--you must receive specific scores or complete everything to get the 100, the requirement is 100) and I leave the status alone--sometimes my modules report weird, the same module for two people will say passed for one and completed for the other, so one gets credit and the other doesn't, which I don't want, so I just go with the grade only.
There used to be a couple settings that if set nothing worked right (or the way I wanted it to)...but now that I'm looking, I don't see them...must have been 1.9 (the dark ages).
And now the short answer--grade reporting is a tricky balance of Moodle settings and SCORM settings and they have to work together.