We re-installed the file module again, and once again, it made all images disappear. Keep in mind, this isn’t just the images not-rendering on the page (like when you forget to sync files), but when you go to the individual content entries, the custom file field is completely gone.
We did find one more clue during this process, though. After re-installing the file module, we tried to use the file manager, and got this result:
The menu that in a normal 2.5.3 installation has this pattern:
content > files > file manager
But when we upgrade (from 2.1.1 to 2.5.3), it renders like this:
content > file manager > nav file manager
And if you choose “nav file manager” it gives PHP errors like this:
A PHP Error was encountered
Severity: Notice
Message: Undefined index: cat_group
Filename: cp/content_files.php
Line Number: 567
We’ve rolled back to 2.1.1. We’d eventually like to upgrade to 2.5.3, but won’t attempt doing it again until we have a much clearer expectation of how we might be able to fix this issue.