Shareholding in CS01 changes? Fatal 9999 Duplicate ShareholdingId: error

I have been testing a submission using the new CS01 schema. The submission including a shareholding list is accepted using the previous schema (ConfirmationStatement-v1-3). However now that I am testing the ConfirmationAndVerificationStatement-v1-0 it immediately and consistently refuses to allow me to file and gives me several 9999 fatal errors with the error code “Duplicate ShareholdingId:”.
It also gives me one 9999 fatal error code with the error message "ShareholdingId is not used, no Shareholder references the ShareholdingId: "
Has something changed? Also, can I test the new schemas using the standard test gateway or must I use a sandpit endpoint? Thanks for any replies.

You can not test the 18th November schemas via the normal test service.

For these, the test instructions are as follows:

You can use your live presenter credentials - but show Package Reference as 0012 and Test Flag as 1.

Endpoint: https://xmlgw-sandpit-staging.companieshouse.gov.uk/v1-0/xmlgw/Gateway

If you receive an XML schema validation error, then the schema is failing due to a syntax error or incorrect basetype compatibility - and should be considered a failed test.

If you receive any other error response, such as an authorisation failure, then that means the schema has passed the schema validation stage, and should be considered a successful test.

For reference, the following is a link to the test service schema page.

https://xmlgw-sandpit-staging.companieshouse.gov.uk/SchemaStatus

SDN

Thank you very much for this, Simon. Much appreciated.