At 2024-10-03T11:26Z a warning triggered an investigation of an increase in the error rate for authorizations. The investigation showed that we were receiving a subtle amount of declines from issuers reasoned with “format error” starting 2024-10-02T05:45Z. These rejects are normal and have numerous times shown issuers to be misbehaving – which is why we have a non-zero threshold that must be met before we become aware.
Together with the “format error” must be an identification of the malformatted field. This led us to identify an issue with an update we applied during 2024-10-02 resulting in AUD authorizations to be consistently declined in the time span 2024-10-02T19:55Z - 2024-10-03T17:05Z.
This, however, only explained a minority of the declines. The remaining declines indicated a field that we have never populated, however, since our investigation indicated it to be an issue across multiple issuing banks, we quickly implemented a change to populate the field.
Both a fix for AUD and for populating the extra field were deployed, and they turned out to fix both issues. The field population issue caused sporadic declines in the time span 2024-10-02T05:45Z - 2024-10-03T19:08Z.
In summary, the two issues above caused an average 0.15 percentage point drop in approval rate in the time span 2024-10-02T05:45Z - 2024-10-03T19:08Z.
We will work hard to identify how the AUD error could happen and will ensure to introduce checks to avoid a similar error to happen in the future. We will also try to work with issuers to identify the cause of the rejects based on the previously unpopulated field.