Hi Kelby,
If I understand right you are looking for a solution for a specific customer. First check if maintaining incoterms is mandatory in master data. If it is not mandatory to maintain, go to the customer master of this specific customer and in the Billing Documents tab of customer master sales area, remove the incoterms and make them blank and save.
In IDoc EDI ORDERS01 pass incoterms values only in Segment E1EDP17 and nothing in E1EDK17 and give it a try.
I am assuming at order level inco-terms at header level are not made mandatory.
My approach is, let the system not propose incoterms from master data, then do not populate incoterms at header level and ensure different incoterms are populated only at item level.
Let me know if this approach works for you.
Thanks
Nagaraj