When you migrated the site to another server, you got a copy of the current production code, an sql dump of production DB imported into a DB on the other server, *and* a copy of the moodledata directory (incuding filedir where the files are really stored) to the other server.
Is that correct?
The error really has nothing to do with permissions/ownerships on files in moodle code nor in roles of users on the cloned system. All about moodledata/filedir/.
In config.php of the cloned system, where does the line for $CFG->dataroot point?
'spirit of sharing', Ken