Operation &1 requires milestone confirmations

What causes this issue?

Operations that require milestone confirmations are not supported for
shop floor orders.

System Response

When creating a production order that contains operations with milestone
confirmations, the system does not set the shop floor order status. The
same applies if you want to change a shop floor order and you include an
operation with milestone confirmations. In this case, the system does
not allow you to save your changes.

How to fix this error?

If you want to create a shop floor order, remove operations that require
milestone confirmations from the routing. And when changing an existing
shop floor order, change the operation control key so that the operation
does not require milestone confirmations.

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.