In bulk-scheduled-process.php, you're missing a slash in line 57 (compare to line 23 in pic-process.php). This is causing images to be saved as e.g. "active-directory-thumbnailsgrant-prudlow1.jpeg" in wp-content/uploads when using the bulk import script. The DB is updated with the intended path, so it 404s.
Since you've got the same adt_get_user_photo() function in both pic-process.php and bulk-scheduled-process.php, I recommend pulling it out into its own include shared by the two scripts.