We were alerted to an issue with one of our downstream carriers that provides traffic to the US. Affected clients would have seen error codes 500 and/or 603 or calls would have started and noise would have been heard. This was due to a codec error from the carrier.
In total, the carrier handled less than 10% of all calls to the US and only a fraction of those had errors.
We are working with the provider to understand the issue and ensure that we can mitigate them going forward.