Compare the send references first. A retry after a timeout, two running jobs, or duplicate handling in your application can create separate sends. A repeated webhook alone is not proof that WhatsApp delivered the message twice.
Trace whether there were one or two accepted send requests. Where the action supports idempotency, retry the same intended action with the same key rather than generating a new one. Pause the duplicate sender and report the references and times to support. Share redacted logs, not API keys or a complete customer conversation.