3691837 - Error: "Schema Validation failed for cXML-0000-ConfirmationRequest with Error Code : CIG-PLT-00623" for confirmation request documents.

Confirmation Request documents created in S/4HANA are failing in Managed Gateway for Spend&Network with the error:

Schema Validation failed for cXML - 0000 - ConfirmationRequest. Suggested Action: Please check the attachment for error details. For implementation guidelines, refer to the corresponding specifications at Managed Gateway for Spend & Network Portal → Resources → Implementation Guides. For further assistance, contact Managed Gateway for Spend & Network Support with Error Code: CIG-PLT-00623.

When error logs is downloaded, there is validation error: 

Invalid content was found starting with element ‘ScheduleLineReference’. One of ‘{ComponentConsumptionDetails, Comments, Extrinsic}’ is expected.

CIG-PLT-00623, ConfirmationItem, ConfirmationRequest , KBA , BNS-ARI-CI-SUP-AN , Managed Gateway for Business Network Sell Side , Problem