My company has a native Android app that uses the GraphQL Storefront API via the MobileBuySDK to create and complete checkouts using the checkoutCompleteWithCreditCardV2 mutation.
A couple of time now (7 times in the past month) we've received error logs for a failure when parsing the mutation response when completing the checkout. The cause of this failure appears to be that the payload returned by the mutation has both a null payment field AND an empty customerUserErrors.
The documentation for the method doesn't state this explicitly, but I would assume that a null payment is the result of some kind of failure/error and should be accompanied by at least one entry in the customerUserErrors giving some indication of what went wrong.
Our app successfully completes around 50-100 checkouts daily, so I don't think it's a problem with our core logic, and the frequency at which this error occurs makes it difficult to reproduce and debug it ourselves.
Has anyone else encountered this problem before, and is there some additional documentation available that explains why this happens?