When a teacher is editing a section or activity, if another teacher modifies the course, the teacher who was editing the section or activity may be returned to the wrong page.  This is due to the section return being stored as the section number.  Even storing the section return as the section id wouldn't completely fix this problem, if an activity or subsection were moved to another section during editing.  Instead storing the type of page to return to (course top level, section, or subsection) would fully resolve this.  The course layout / course display setting would provide appropriate options for this, if a third option were added for subsections.