To replicate: 1. Enable the system preference Autobarcode. Select incremental EAN-13 barcodes. 2. Add a subscription to a bibliographic record. Be sure to select the option to create item records when receiving. 3. Receive an item. Click in the box for barcode and see the barcode autofill. Save 4. Receive a second item. Click in the box for barcode and see the previous barcode is inserted. Save fails because of the duplicate barcode. I would expect the barcodes to increment properly. Tested on 25.05 in a sandbox.