I have several custom post types where I use MetaBox, and all of them use "file" type fields. These fields include the ajax delete function to remove uploaded files. The way I have used these fields for each CPT is the same.
On two of the CPTs the ajax file deletion works as expected. However, on one CPT I get an alert that pops up saying "Invalid File" when I try to delete files.
I have done some initial troubleshooting, and see what the problem is, but I haven't tried to fix it yet.
In the file inc/fields/file.php there is the following line: