@ZoteroCalbrNote:
It adds the empty books because it could not find the file attachments, and the options checkbox said to do that. That is why you see the calibredb command line parameters in the debug log.
If you copy and paste the following entry into Windows to see if Adobe Acrobat executes it, what happens? This is to test the CSV file attachment path validity...
Code:
C:\Users\Steven\AppData\Roaming\Zotero\Zotero\Profiles\2yjmvims.default\zotero\storage\9SGK8X4W\0697.pdf
DaltonST