After a recent upgrade from 2.6.1 to 2.9.2 we now realize that no one can edit uploaded files. When in the File Manager and clicking on either the “Edit file” or “Edit image” button the user gets a “You are not authorized to access this page” error. The user can upload images however. Permissions have been checked and rechecked and are set at 777.
As a side note this seems to be causing issues with all images in a Matrix field not being displayed.