ISO program calling oe_order_pub.Process_Order to change warehouse

Dear All

We are using an ISO program to generate ISO. In program we are changing warehouse in original sales order using oe_order_pub.Process_Order api but in some cases where ATP override flag is checked api is throwing error:

You are not authorized to modify scheduling attributes on a overriden line

However when I try to change warehouse from front-end even ATP override flag is checked it allows me change warehouse.

Why api oe_order_pub.Process_Order is throwing error for overridden lines?