I have a customer with: main office has an MBX + Comcast PRI, VoIPed to 4 other sites, all of which have XTS + various providers. One of them uses Comcast PRI also. When they intercom over the VoIP, everything works fine EXCEPT when the main office is involved -- they are sometimes getting half-duplex conversations ("I hear them but they can't hear me"), and some dropped calls. There is no pattern to either failure - it is intermittent but ongoing.
Vertical Tech Support advises us to tell the customer "not to use Comcast, our equipment won't always work properly with their emulated PRIs".

Is there any fix for this?
Anyone having any success or complete failure with Comcast's emulated PRIs?

Thanks as always for your help.