I have several systems running IncrediblePBX 13-12 on RentPBX, and using Aastra 6757i phones. I have a problem with one system where some phones periodically go to "No Service". The office has Xfinity 1GB service with Static IP, and their box set to pass-through (bridge) mode. Then I have a Netgear router handling the in-house networking. I have SIP ALG set to Off. Anyone have any thoughts as to why the phones go off line at random? Thanks.