Is this code located inside an onCreate() method or onResume() method of the CheckoutActivity? Or some button click listener? If not, where? We want to understand the entry point that leads to the code you shared with us.
Do you see your code getting executed again right after the attempt to make a payment fails? As if it retries to make a payment? Logs we see on the device suggest that startCheckoutActivity was called at least two more times after first attempt to make a payment failed. Was is a result of user interaction or a retry mechanism in your code? 