I just had a teacher report that in an assignment where he is sure he uploaded feedback files for the students, many of those feedback files are now missing.
He is sure the original upload worked, since many of the students actually incorporated the feedback files into their updated submission. He is also a rather competent user who uses submissions and feedback files extensively and never had this problem.
Log files show that the grade for the submission was updated after the initial feedback, whether feedback files are uploaded or deleted is unfortunately not a part of the logs.
Did anyone ever had this happen or know any bugs in browsers or Moodle that could lead to an original feedback being overwritten?