Order &1 item &2 must be processed manually

What causes this issue?

You are using dynamic assembly.
The system has generated production or process orders. The sales order
item is now cancelled.

System Response

The production or process orders cannot be processed automatically.

How to fix this error?

Check and process the production or process orders manually.

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.