The Inventory Profit Margin report is not useful for troubleshooting, because you cannot drill down on various figures. Possible approaches are to drill down from the Summary on the Inventory - sales and/or Inventory - cost accounts to see what makes them up. There, you will have access to actual transactions.
Another approach is to narrow the date range of the Inventory Profit Margin report until the problem disappears. Then, you will know exactly what date the problem transaction was entered, making it easier to find.
You can also create an Inventory Value Summary report and then narrow its date range.
Finally, assuming you sell this item with sales invoices rather than receipts, you could generate a Sales Invoice Totals by Item report and drill down from there to transactions.
You are looking at a drill-down result from the Accounts Receivable column for one customer in the Customers tab. Color differences for that page are now limited to the balance of the account. If the balance is negative, the color will turn red.