System intermittently not answering calls

System is configured with a Sangoma 4 port FXO card, no IP trunks and Asterisk 11.14.2 , core 2.11.0.34, framework 2.11.0.43, dahdiconfig 2.11.52

The system has been installed for some time and working properly for the most part. Get the odd call from someone that says they called into the system, rings once then drops the call. It’s very random and really hard to pin it down.

Recently this was reported and I found a couple of call records that could have been the issue.

The numbers are terminated at voip.ms and are call forwarded to an analog line into the office, so I have a log or cdr record of the calls inbound. In the voip.ms cdr the calls in question show as not answered and 0:00 seconds in length, then you can see the caller call in again, then again. First call comes in at 00:22:12, then again at 00:24:03, again at 00:24:43, then finally at 00:27:52 the call gets answered

Here’s from the Full log from that time period…

[2015-07-07 00:06:02] VERBOSE[3032] asterisk.c:     -- Remote UNIX connection
[2015-07-07 00:06:02] VERBOSE[3032] asterisk.c:     -- Remote UNIX connection
[2015-07-07 00:06:02] VERBOSE[18802] asterisk.c:     -- Remote UNIX connection disconnected
[2015-07-07 00:06:02] VERBOSE[18802] asterisk.c:     -- Remote UNIX connection disconnected
[2015-07-07 00:19:01] VERBOSE[3032] asterisk.c:     -- Remote UNIX connection
[2015-07-07 00:19:01] VERBOSE[3032] asterisk.c:     -- Remote UNIX connection
[2015-07-07 00:19:01] VERBOSE[18881] asterisk.c:     -- Remote UNIX connection disconnected
[2015-07-07 00:19:01] VERBOSE[18881] asterisk.c:     -- Remote UNIX connection disconnected
[2015-07-07 00:27:23] VERBOSE[18962][C-00000efb] sig_analog.c:     -- Starting simple switch on 'DAHDI/1-1'
[2015-07-07 00:27:23] VERBOSE[18962][C-00000efb] sig_analog.c:     -- Starting simple switch on 'DAHDI/1-1'
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Executing [s@from-analog:1] NoOp("DAHDI/1-1", "Entering from-dahdi with DID == ") in new stack
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Executing [s@from-analog:1] NoOp("DAHDI/1-1", "Entering from-dahdi with DID == ") in new stack
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Executing [s@from-analog:2] Ringing("DAHDI/1-1", "") in new stack
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Executing [s@from-analog:2] Ringing("DAHDI/1-1", "") in new stack
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Executing [s@from-analog:3] Set("DAHDI/1-1", "DID=s") in new stack
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Executing [s@from-analog:3] Set("DAHDI/1-1", "DID=s") in new stack
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Executing [s@from-analog:4] NoOp("DAHDI/1-1", "DID is now s") in new stack
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Executing [s@from-analog:4] NoOp("DAHDI/1-1", "DID is now s") in new stack
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Executing [s@from-analog:5] GotoIf("DAHDI/1-1", "1?dahdiok:checkzap") in new stack
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Executing [s@from-analog:5] GotoIf("DAHDI/1-1", "1?dahdiok:checkzap") in new stack
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Goto (from-analog,s,9)
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Goto (from-analog,s,9)
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Executing [s@from-analog:9] NoOp("DAHDI/1-1", "Is a DAHDi Channel") in new stack
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Executing [s@from-analog:9] NoOp("DAHDI/1-1", "Is a DAHDi Channel") in new stack
[2015-07-07 00:27:24] VERBOSE[18962][C-00000efb] pbx.c:     -- Executing [s@from-analog:10] Set("DAHDI/1-1", "CHAN=1-1") in new stack

if you look at the time stamps in the cli output, there are no records for the time period in question, other than the UNIX connected and disconnected messages.

Is this typical behavior or is there something I should be looking for?

Thanks in advance!