When one cancels a hold with the Cancel button on Holds Awaiting Pickup (waitingreserves.pl), a transfer may be generated but Koha doesn't prompt you to print a transfer slip. Following the changes in bug 23092, this transfer is generated with both a daterequested and a datesent -- in other words the transfer is immediately considered Sent. Since the transfer is already Sent, checking the item in to generate a new hold slip will generate a "wrong transfer" error message, cancel the first transfer, and generate a new transfer (which does get a slip). I see two options to resolve this: 1: We could generate the transfer as Requested rather than Sent. One would then check the item in to trigger the transfer and get a slip at that point. 2: We could print the transfer slip right away when cancelling the hold. Answer 1 seems simpler and more in line with the directions transfers are going in.
Could an option to 'reprint' the transfer slip instead of the wrong transfer message also be an option here? I think you can usually print the hold slips multiple times, so I don't see why we should not do the same for the transfer slip.