Analytics API 500 on Custom Segment Export

Need some help troubleshooting…

GET /api/v2/analytics/conversations/details/query failing with 500 Internal Server Error when filtering by specific custom segment ID. Works fine for standard segments.

{
 "code": "internal.server.error",
 "message": "Failed to execute query against analytics backend"
}

GC CLI v2.3.1. Segment exists and has data. Any known backend issues in Sydney region?