Operation control key &1 cannot be used with an MES

What causes this issue?

The order is intended to be distributed to an MES. It contains
operations with the control key &V1&, for which milestone confirmation
is allowed or for which confirmation is prohibited.
However, in the case of integration with an MES, confirmation must be
possible for every operation. A milestone confirmation can lead to a
situation in which operations for which provision has been made for a
separate confirmation from the MES are automatically confirmed.

System Response

The system terminates the saving of the order.

How to fix this error?

If necessary, choose a different control key for the relevant operations
of the order.

Procedure for System Administrators

You can check the settings of the control key &V1& in the
<DS:SIMG.SIMG_CFMENUOLPFOPJ8>Implementation Guide</>.
You can likewise influence the properties of this message in
<DS:SIMG.SIMG_CFMENOLPFOPJB>Customizing</> and thus suppress it if it is
not relevant to your business process.

Error message extract from SAP system. Copyright SAP SE.