Hi J Lane,
Have you got the solution of your question?
I am also facing the same problem. can you plesae let me know how you resolved you issue?
In our case the issue was identified as a bug
Issue identified as a bug...' BUG 19134232 - SHIP-TO LOCATION DOES NOT DEFAULT CORRECTLY AFTER PATCH 17774755', the issue can be resolved by upgrading PO_PDOI_LINE_PROCESS_PVT.plb to 120.58.12020000.18 or above.
Solution: Apply patch 19879160:R12.PO.D.