Log in as admin Create a course Obtain the ID of one of the empty course sections (e.g. using the Permalink section action and copying the numeric value from the URL) Run the following query on your DB: UPDATE m_course_sections SET sequence = NULL WHERE id = <SECTIONID> Select More > Course reuse from course navigation If Backup isn't already selected, press/select Backup (behaviour differs per version) Confirm there is no deprecated warning regarding explode()