Root Cause

• Duplicate transaction attempt: The customer likely clicked the payment button multiple times, initiating multiple requests with the same token.

• Token reuse conflict: The same token is being used for multiple concurrent transactions, which the payment gateway does not allow.

• Slow network response: The initial transaction is still being processed due to delayed responses, causing subsequent requests to fail.

• Lack of idempotency handling: The integration does not handle repeated clicks or multiple submissions gracefully.

Troubleshooting and Solutions

• Advise the customer to wait for the first transaction to complete before attempting again.

• Inform the customer to avoid clicking multiple times on the payment button.

• Implement client-side controls to disable the payment button after the first click until the request completes.

• Use idempotency keys in your API calls to prevent duplicate charges and manage concurrent transaction requests effectively.

• Monitor transaction logs to ensure only one successful charge is processed for the token in use.

• If it's occurring quite often, reach out to the Chargebee support team with sample logs for further investigation.