Delete Attachment API is not working when PO Change Order is in Incomplete Status

API we are using - Delete an Attachment

/fscmRestApi/resources/11.13.18.05/draftPurchaseOrders/{draftPurchaseOrdersUniqID}/child/attachments/{attachmentsUniqID}

This API is working when newly PO at revision 0 are in Incomplete Status. But it is not working or Deleting any file when PO Change Order is in Incomplete Status.

As the Error is showing - Cannot perform the Action as PO is in Open Status

Is there anyway we can delete the attachment during PO Change Order or on new PO Revision.