WebRTC connection drops at 150 concurrent users

Just noticed that the WebSocket handshake fails when pushing past 150 simultaneous softphone sessions in the load test. The client logs show a generic disconnect without a specific error code.

{"error": "Connection reset", "code": 1006}

The API rate limits are untouched, so this looks like a hard cap on the media channel capacity. Is there a known threshold for the free trial or sandbox environment regarding concurrent WebRTC streams?