Webchat Bot Fails to Initialize During High Concurrency Load Test

Can’t get this config to load properly… The Webchat bot fails to initialize when JMeter pushes concurrent sessions above 200 in the ap-southeast-1 region. The WebSocket handshake completes, but the initial bot prompt never arrives. The server returns this error in the debug console:

{"error": "bot_init_timeout", "code": 504}

Is there a specific rate limit on the /v2/conversations/messaging endpoint for bot triggers that I am missing?