I just saw the thread that voxabox referenced. UDP timeout of 10 seconds seems low. I am not familiar with Tomato but I assume this is the NAT entry timeout for UDP packets. Since the NAT send alive interval for PAP2T is 15 seconds, you will have a 5 second window where the NAT entry will not exist. And you will have problems getting incoming calls during that window.
1bird2, play around with the value and make sure incoming works fine.
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