Installing and upgrading help

I resolved this by going back to the beginning and upgrading one version of moodle at a time from 2.8 through to 3.3 which worked. I did have to manually add the field course_id to the mdl_feedback_values table at the upgrade from 3.0 to 3.1 but once that was done it all worked fine. Making the changes suggested (adding the large prefix info) did not fix the problem when I upgraded directly from 2.8.5 to 3.3 so there must have been something in that direct upgrade that skipped something important in an earlier version.