I think there is somethong wrong in the approach.
despite the fact that there are better ways to get the total (like a calculated fiedl equal to Production Report::sTotalQty), I added other records and the FailedOrderTotal does not change (it remains 67).
I think that you create the FailedOrderTotal field having already the 2 records in product. FM enter the totals but never updated it.
With all looked up value fields, changes to the source table (production report) do not automatically update values in this field in the Job Summary table. This is standard, expected behavior for looked up value fields, been that say since fileMaker 3 was released and we could finally link tables in relationships. To update the displayed totals in such a looked up value field after such changes are made, you'd need to put the cursor in the key field (salesOrder) and choose relookup from the records menu (updates all records in current found set) or re-edit the key field (updates just the current record).
Keep in mind that this file demonstrates an unexpected result. It is not intended to suggest a best approach for the design of any specific database. Sometimes you need such subtotals to update as the source data changes and sometimes, (such as product prices in a products table), you do not. FileMaker gives you both options. You just have to pick the method that works for you.
You may find this discussion of both approaches useful: Auto Fill