Rescheduling Sales Order Fulfillment When Supplier Delivers Early in Back-to-Back Purchasing

We are using Back-to-Back Purchasing. After creating a purchase order, the supplier happened to deliver earlier than the promised date. Our customer prefers earlier delivery and was not fully satisfied with the original promised date, so we would like to bring forward the scheduled ship date.

However, when we try to reschedule from the sales order fulfillment line, the supply order ends up in an error state. If we cancel the supply order first and then reschedule, it seems to work. But this feels like a complicated operation for what we are trying to achieve.

Questions:

1. What is the recommended or best practice operation in this scenario? Is there a simpler or more appropriate way to bring forward the scheduled ship date when the supplier delivers early?