UPDATE: The fix for this issue was released in the August 31, 2018 update.
Known Issue - The Master Schedule process to Copy a section is not working correctly to Copy or Move Students before Attendance (ATT) and Course Attendance (CAR) is initialized. A section can be copied when using the "Do not copy/move Students" but when trying to Copy or Move students, the process does not complete. Programming is looking into this now.
Work Around - a 2 step process can be done to Copy/create a new section and then copy or move the students into the new section:
The process works correctly once Attendance (ATT) and Course Attendance (CAR) is initialized.