feedback

What could be the reason that feedback that a teacher has given to a student at a submission point, differs in text and letters from what it should actually be? Normally, that should be the same. The only thing I can think of is that it is due to the student's laptop, but then the student should encounter it more often. I have advised the teacher to let the student go to the feedback via a different system.It cannot have been adjusted by "someone" because then the teacher must also see the adjustments and that is not the case. I cannot think of anything that causes this to happen.