If you import MARC bibliographic files, duplicates barcodes will result in failure to import this particular item while the record will still be imported. The general information is shown in the job detail report ("Number of items ignored"), but it is not possible to identify the specific items with this problem. It would be beneficial to show this issue in the detailed view ("Manage imported batch") to identify the problematic items. This could be applied to other import problems for items.
Related to bug 32638
+1