Delivery note problem

We have 2 Item code numbers WAP321-E-K9 ( Valuation method is Moving Average) and WAP321-E-OLD (Valuation method is FIFO).
The WAP321-E-OLD is the active item code number, and we issued some purchase and sales invoices from WAP321-E-OLD.
The WAP321-E-K9 is not an active item code number, we don’t issue any invoices from this.
now I want to make “Delivery Note Return” from WAP321-E-OLD but this error is showing. We think this is software problem. How do we solve it?


Can you please share the screenshot of original item selected in the Delivery Note? Did you merge these two items by any chance?

We used the item code number WAP321-E-OLD when we made the delivery note and sales invoice to the customer