Thanks for your thoughts in advance on this strange occurrence.
We're a Moodle 2.3.3+ site (though I've taken a copy of the course into a dev site and upgraded all of the way to current 2.6 where issue still present) and we're finding that some (a growing number as it is grading review time) courses which would have been upgraded from pre 2.3 assignment module to 2.3 module are missing 'submissions', 'grades', and 'feedback' though if you click to download all of the submissions you get lots, and the summary suggests they are submitted fine and don't need grading.
I just found one user where it said no submission but once I'd clicked on them it suddenly found their submission but still no grade or feedback.
I've tried a course backup -> restore onto another system to no avail.
It's quite odd how the grades.xml shows the details of the grades, and feedback.
Any ideas very gratefully received.
Many thanks in advance for your thoughts.
PS. The screenshots show a single user with a grade as I'd found somewhere else on the forum about making a change may bring others back.