You have used the same QRCode in two different TOCs in the same TextBook.
The QR Code can be linked only to one TOC, hence the system is showing you the error.

Please check the CSV file and make sure that  you have not used the same QRCode in multiple rows.  If you find the QRCode in multiple rows in the same CSV, please remove the QRCode from one of the rows and  use a different QRCode