Assignments teacher's typed text not saving with returned work

I wonder if anyone has any insight into this issue we are having. A teacher has used Assignments to set some work for students. The assignment was turned in as a Word document. He added some in-line comments using the 'Comments' feature in work and those are saved. He also typed some extra text and coloured them in red at the end of the student's essay. When he returned the work via Assignments, the 'comments' were preserved, but the text he typed at the end of the student's work was cut off and the formatting was removed. Is there some restriction to being able to annotate to the end of a student's Word document? The essay is not long, less than two typed pages. Any suggestions for what is going on here would be greatly appreciated.