Several planning systems are relevant for production order &1

What causes this issue?

The complete withdrawal requires exactly one system for each combination
of material and plant.

System Response

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

How to fix this error?

Adjust your integration model in such a way that the combination of
material and plant only exists in <ZH>one</> active integration model.
You can enter this error message as a warning in Customizing for
<ZK>Logistics - General</> under
<DS:SIMG.MPWALL_OMILL_T160M>Define Attributes of System Messages
</>.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.