Payment scheme &1 may not include contract account items

What causes this issue?

You cannot include contract account items in payment scheme &v1&,
because payment scheme &v2& already contains contract account items.

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?

Use payment scheme &v2& for all the contract account items, or remove
all contract account items from payment scheme &v2&, and include them in
payment scheme &v1&.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.