TechMB,
No, the phone mirror shouldn't be causing an issue as it just allows one port to see what is going on with the another port. Personally, I have never had an issue where that was a problem.
Those are pretty much the default settings except I believe that your DTMF Encoding should be set to RFC 2833, but that has nothing to do with your issue.
If you press F1 it should explain what each field does and how to adjust them to "hopefully" alleviate, read not fix, any issues you may be experiencing.
As for the Insufficient Bandwidth issue it is controlled by two settings within this Call Configuration.
1. Audio Diagnostics Sampling Period
2. Average In Time Frame Percentage Threshold
Basically if during the sampling period the average amount of data does not exceed the Threshold an Insufficient Bandwidth alert will be sent out. Does this mean that they are having audio issues, not always, but it is a good indicator. By default I have changed mine to 45% as that would indicate a serious issue.
On a different subject, why do you have port 5060 opened up? Do you have a SIP device accessing the phone system from outside the network?
Thanks,
TE