Calls drop from BYOD at 29:28, ATA works normally

Hi

Outbound calls to toll and toll-free AT&T Connect conference numbers are consistently ending at 29:28 on multiple BYODs. Calls to the same numbers via my ATA do not drop.

This behavior started on October 5. I have tried various settings with no success--every call hangs up at 29:28. Calls to CallCentric, where I have an old test account, work normally (no hang up). Calls routed through both the cable modem and 3G wireless behave identically: both drop at 29:28.

I'm using CSipSimple (Nightly 1952) with Android 2.3 and 4.1 (Cyanogenmod).

I tried using the native Android Internet Calling client instead of CSipSimple. This worked once, but DTMF tones fail to work on most attempts. I also rolled CSipSimple back to a version used successfully two weeks prior to October 5, no success there. CSipSimple did work once, too, on October 7, but all other CSipSimple calls since Oct 5, about 20, have dropped at 29:28.

The destination IP addresses from firewall logs for each type of connection (ATA, CSipsimple, and native Android) vary as shown here:

Android (LG P930) 4.1: 67.228.190.147
Android (LG P930) 4.1: inbound 174.36.46.51

Android (HTC Liberty) 2.3: 67.228.190.148
Android (HTC Liberty) 2.3 using native Android client: 174.36.46.51

Linksys ATA: 156.154.70.1, 156.154.71.1, 50.97.129.83

I tried different DNS resolver settings in CSipSimple, but that did not change the destination IP address.

I had a similar problem for particular numbers where calls to particular numbers would drop in 0:30 (thirty seconds). That was fixed by tech support. I cannot prove this isn't a client problem with Android or CsipSimple, but my prior experience and the different IP addresses could indicate a problem at the VoipO end.