Delivery block is determined in the schedule line category.

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The delivery block is determined by schedule line category.

What causes this issue?

You have set a delivery block on both billing plan type and schedule
line category.

System Response

The system determines the delivery block by schedule line category.

How to fix this error?

You can manually change the delivery block in the sales document. You
can also change the setting for delivery block in schedule line
category.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.