TW,
for the third party process I configured two order types, for local and export sales. I copied the standard order type in the system for both order types. Likewise there are two billing types for both order types. for both I copied F1.
third party material is constant but the standard material is different.
The only major difference between the faulty orders and the good orders is that the billing date for the faulty orders is at a later date from when the order was created. That is the order might have been created in May and billing done in July.