Contact person cannot be deleted because used in EAM order &1

What causes this issue?

You want to delete a contact person. The contact person is used in plant
maintenance data.

System Response

The contact person cannot be deleted.

How to fix this error?

Remove the contact person from plant maintenance data first. If the
contact person is used in completed orders, you can either cancel
technical/business completion, remove the contact person from partners
and complete the order(s) again or archive the order.

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.