Haso,
You led us on the path to fix this huge issue. Thank you so much. We are trying to update OrderRel using similar code to your post, and when we created our method directive on the ImportEDIPostProcessDemand, we still were getting blanks on PartDtl.DueDate. We certainly may not have gotten the code correct, but the OrderRel.ReqDate wasn’t updating for new releases.
After several tries and iterations, we had not have eliminated the blanks, so we checked out https://www.epiusers.help/t/mrp-suggestions-for-unfirm-releases/67060/10
This let us know we could update PartDtl directly without any bad repercussions. So, we put a Data Directive on DemandHead.InTransaction that updates the DemandSchedule, OrderRel and PartDtl on each import. No more blanks, no more duplicates and all of our new Order Releases have a PartDtl that matches at ReqDate to DueDate.
I’ll post the data directive after this, in case it can help anyone.