This may or may not help but I just had some very weird problems for a week or two on an IPO with a PRI; it wasn't audio
problems but a lot of other static and issues, and after fighting diagnosing it for a week, I went there, and unplugged the
AT&T equipment myself and left it for a few minutes, then plugged it back up. Problem solved. AT&T had certified remotely
that everything was good twice.