Hi experts,
1. I extend Sales Order and Outbound Delivery.
2. In the BeforeSave event of OutboundDelivery.xbo, I update the extension field of SalesOrder.xbo.
3. I am getting the error "The field is Read-Only" .
I am guessing the problem is because of being different Deployment Units.
But I don't know how to solve it. 
Any idea please.
Best Regards
Fred