WebRTC handshake failures at 3k concurrent users in AP-Southeast-1

Trying to understand why our JMeter load tests for Genesys Cloud softphones in AP-Southeast-1 start failing with WebSocket 1006 errors once concurrent sessions exceed 3,000. Using the latest JS SDK and standard REST API v2 for authentication, but the connection pool seems to exhaust before the media streams stabilize. Any insights on specific WebSocket connection limits or timeout configurations for this region? Thanks.