Contract release order possible for one contract only

What causes this issue?

You want to create a scheduling agreement item with reference to
contract &V1&. However, the scheduling agreement already references
contract &V2&. A scheduling agreement can can only reference one
contract.

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?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.