13111: Annotate: Annotate must contain only one of element X

This error occurs when Twilio processes an <Annotate> instruction that contains more than one instance of a nested element that is allowed only once.

• The <Annotate> block includes the same child element more than once.
• Your application generated duplicate annotation elements while building TwiML dynamically.
• Two XML fragments were combined into a single <Annotate> block and created a duplicate child element.

• Review the <Annotate> block and keep only one instance of each supported child element.
• Inspect the final TwiML returned by your application and remove any duplicate nested elements before sending it to Twilio.
• If you generate TwiML with templates or helper code, update that logic so each annotation field is added only once.

• TwiML for Programmable Voice
• Voice Insights overview
• Call Annotation Resource