Assignment materials not appearing

The Teacher has made a post with 2 assignments attached.

The student can see 2 assignments, but the documents don’t show up - they are listed as untitled.

The documents are in the materials area, but not connected. This effects about 1/3 of students, not everyone...

Has anyone else seen this or know how to cure it?

The School is publicly listed on iTunes U.

The Teacher Apple ID is registered with the school.

The iOS was up to date on version 8.4.1 and iTunes U app was up to date.