It does not process the bulk uploading image(s) if:
- The (ftp) uploaded image has a space in the file name
- If the (ftp) uploaded image has a mix of Upper and Lower case letters in its file name
- If the uploaded image (ftp) has a mixture of the above.
I do not know if you are aware of this or not, so I thought it prudent to mention it.
It still uploads the image but does not process a thumb nail for it, or make a place on the catorgory for it (as there is no thumb nail)