Exporting PBI report to pdf file via REST API - cannot load model

Hello, 

I'm trying to export pbi report to pdf file using REST API 😞https://api.powerbi.com/v1.0/myorg/groups/{groupId}/reports/{reportId}/ExportTo) and so forth.

and I successfully can when the report has no RLS defined on it.

If it does then the pdf file generated contains error message, such as:

"Cannot load model", etc., please view attachment below.

This is the body format that I'm sending with my request when trying to export a report with no RLS:

$body = '{ format : "pdf" }'

But when a report with RLS is sent to be exported then I need to append identity within the body, otherwise it would complain that no identity was specified.

$body = '{
format : "pdf",
powerBIReportConfiguration : {
identities : [{ username : "[email protected]", roles: [ "role" ], datasets : [ "a5f0xxx--yyy-zzz-zzzf1da6916" ] }]
}
}'

I've tried multiple users, all of them having assigned the role and all of them capable of viewing the PBI report itself including data when accessing it via PBI Service.

Any ideas, please, what should be set for this to work?

Thank you.

Marcel