VAPI•3mo ago

Frequent Call Terminations Due to 11labs TTS Errors

Hello Vapi Support Team,

Recently, we have noticed that calls are frequently terminating due to errors related to 11labs TTS. Could you please investigate this issue?

call_ids:
bfc00424-4e59-47ab-9dd3-9dbadf368529
1e982742-9ab3-4cb0-96df-83e275356e7c

Additionally, we have configured a fallbackPlan to mitigate these errors, but it only seems to work occasionally. We would greatly appreciate it if you could look into why this is happening as well.

Thank you for your support.

Vapi Support BotAPP•9/30/25, 12:20 PM

To ensure your fallbackPlan is configured correctly, double-check that your assistant's voice configuration follows this structure and uses valid provider/voiceId pairs:

{
  "voice": {
    "provider": "11labs",
    "voiceId": "your-primary-voice-id",
    "fallbackPlan": {
      "voices": [
        { "provider": "openai", "voiceId": "shimmer" },
        { "provider": "cartesia", "voiceId": "248be419-c632-4f23-adf1-5324ed7dbf1d" }
      ]
    }
  }
}

{
  "voice": {
    "provider": "11labs",
    "voiceId": "your-primary-voice-id",
    "fallbackPlan": {
      "voices": [
        { "provider": "openai", "voiceId": "shimmer" },
        { "provider": "cartesia", "voiceId": "248be419-c632-4f23-adf1-5324ed7dbf1d" }
      ]
    }
  }
}

Tip: The order matters—Vapi will try each fallback in sequence if the primary fails. Make sure all providers and voice IDs are valid and supported.
For more details, see the voice fallback plan documentation.

Source:

Voice Fallback Plan

⤵️ Mention @Vapi Support Bot for follow-ups 🐥

unexpected-ivoryOP•9/30/25, 12:22 PM

unexpected-ivoryOP•10/1/25, 7:55 AM

I’s happening again today. Sorry but I need you to check it urgently.

call_ids
5a350983-94e9-4e70-ae26-3a00b824bb02
3e664051-957b-4d7b-bc59-3a06482ce207
6b483640-a375-433b-bcfe-5358b9fc1588

KyleAPP•10/2/25, 12:05 PM

Hey! To help track down this issue, could you share:

- When exactly this happened (the timestamp)

- What response you expected to get

- What response you actually got instead

This would really help us figure out what went wrong!

unexpected-ivoryOP•10/3/25, 1:07 AM

Thank you for your support.
The call starts, but the AI assistant doesn’t say anything and the call gets disconnected.
The call ends a few seconds after it starts.
Looking at the call logs, an error with 11labs voice has occurred.

unexpected-ivoryOP•10/6/25, 5:04 AM

Thank you for the support. Sorry but any update?

KyleAPP•10/6/25, 8:53 PM

Sorry it's taking longer than usual. Our team is looking into it and will get back to you with an update soon.

unexpected-ivoryOP•10/10/25, 3:52 AM

Thank you for the support again. So sorry but any update?

KyleAPP•10/14/25, 2:38 AM

This is the error from ElevenLabs that we received in our logs:

🔵 12:13:03:616 ElevenLabs (WebSocket #0) Error: {
  "message": "We are sorry, the system is experiencing heavy traffic, please try again. Refer to https://elevenlabs.io/docs/resources/error-messages#code-429 for more information.",
  "error": "system_busy",
  "code": 1013
}.

🔵 12:13:03:616 ElevenLabs (WebSocket #0) Error: {
  "message": "We are sorry, the system is experiencing heavy traffic, please try again. Refer to https://elevenlabs.io/docs/resources/error-messages#code-429 for more information.",
  "error": "system_busy",
  "code": 1013
}.

The error is due to a bandwidth issue on ElevenLabs side. It could potentially be from a busy time of the day, but if the error is persisting we suggest switching providers to one with higher capacity.

{ "voice": { "provider": "11labs", "voiceId": "your-primary-voice-id", "fallbackPlan": { "voices": [ { "provider": "openai", "voiceId": "shimmer" }, { "provider": "cartesia", "voiceId": "248be419-c632-4f23-adf1-5324ed7dbf1d" } ] } } }

🔵 12:13:03:616 ElevenLabs (WebSocket #0) Error: { "message": "We are sorry, the system is experiencing heavy traffic, please try again. Refer to https://elevenlabs.io/docs/resources/error-messages#code-429 for more information.", "error": "system_busy", "code": 1013 }.

Frequent Call Terminations Due to 11labs TTS Errors

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