This error may occur when reporting a Full Qualification Course (e.g. a Certificate II, a Diploma or a Skill set) to DetConnect using an Enrolment Commencing Course Identifier of '8 - Subject-only training'. Setting this field to '3 - Commencing training in the program' (for each enrolment in the course) will correct this error.
To avoid similar situations in the future we recommend also setting the default values for this field to '3', this is done under Configuration>Default values>Commence.