Please, ensure you can reproduce the reported issue before testing that the patch fixes the problem Stop the unoconv service or remove its path in the admin config. Create an assignment with file upload submissions enabled. As a student, submit a document that would require unoconv conversion. As a teacher, visit the grading page for the submission to generate a blank pdf and page image. Restart the unoconv service or re-enter its path in the admin config. As a teacher, visit the submission grading page again. Verify that the page image(s) are now regenerated correctly.