This is a fairly rare error but you can easily fix it.
Just follow the steps to ensure that no duplicates are created in your Xero account.
1. Please login to your Xero account.
2. Find the item and 'void' it.
3. Login to ReceiptBank and find the item in your Inbox (you can try the 'Advanced search' engine, next to the 'Supplier search' box.
4. Click the 'Tools' button on the menu at the top and choose 'Clear publishing data' option before exporting.
5. Re-publish the item from your 'Inbox' by clicking the 'Publish' button.