WFM Bulk Export API failing for Digital Channel Sessions

Need some help troubleshooting an issue with the Workforce Management bulk export API. We are attempting to pull session data for webchat agents to reconcile legal discovery requests. The environment is Genesys Cloud EU-West with BYOC S3 storage.

The job fails immediately upon creation. We are using the standard endpoint POST /api/v2/analytics/conversations/export. The payload includes filters for type set to webchat and a date range covering the last 14 days. This worked for voice calls last week, but digital channels are now throwing a validation error.

{
 "code": "invalid_request_body",
 "message": "Filter criteria invalid for conversation type 'webchat'. Field 'media_type' is required.",
 "status": 400
}

The documentation does not explicitly state that media_type is mandatory for webchat exports in the WFM module. We have tried adding media_type: "chat" to the filter object, but the 400 response persists. Is there a specific schema update for digital channel exports in the London timezone region? We need to maintain chain of custody for these records, so manual download is not an option.