if the PB device will allow it, slow the modem to anything below 9600 baud. Once 2400 baud is passed, modems are just multiplexing channels, many 2400 baud channels. Slowing the modem speed can remove most common issues, since the fault tolerance at the lower speeds is so much greater. Shoot, we used to use them audio-couplers to get 110 and 300 baud (back in the day)
