Looks like you ran into an active bug possibly. Take a look at: https://tracker.moodle.org/browse/MDL-63231
Does it happen only with SCORM activities? Does the teacher have moodle/course:changesummary capability? Your site might have disabled it and it will give that error. See Paul Martin's post here: https://moodle.org/mod/forum/discuss.php?d=374099#p1510686