Bulk Export 422 on Digital Channel Transcript Metadata Filter

Dealing with a very strange bug here with the bulk export API when trying to pull transcript metadata for digital channels. The job fails immediately with a 422 Unprocessable Entity error.

Environment: Genesys Cloud BYOC (eu-west-1).
Endpoint: POST /api/v2/bulkexports/exportjobs

The request body includes a filter for interaction_type equals digital and channel_type equals webchat. The issue seems to be specifically with the transcript_text field inclusion in the metadata filter. When this field is present, the API returns:

{
 "errors": [
 {
 "code": "BAD_REQUEST",
 "message": "Invalid filter criteria for transcript metadata"
 }
 ]
}

If I remove the transcript filter, the job completes successfully, but the data lacks the full conversation text required for the legal discovery audit. This is critical for chain of custody verification.

Has anyone else seen this specific 422 error with transcript metadata in digital channels? Is there a known limitation or a different field name I should be using for BYOC environments? The documentation suggests this filter should be supported, but the strict validation seems to be rejecting it.

Any guidance on the correct syntax or a workaround would be appreciated.