Test on any device on a 3.3 or newer site. Create an assignment with groups and some students. Send a submission as one of the students. In the app, login in the site as a teacher. Go to the course of the assignment and toggle "Show download options" in the course menu. Download the assignment from the course page (do not access the assignment). Switch to offline. Go to the assignment and open "Participants" submissions. Check that the list of submissions is displayed without errors for al groups. Also check the list of "Submitted" and "Needs grading" submissions.