Intermittent misdn audio problem on queue announcement

I have been repeatedly upgrading Asterisk, and FreePBX in the past year hoping this issue will disappear. Using latest version of both Asterisk, FreePBX, and misdn from misdn.org.

All calls are directed to a queue which normally has a file played back as the announcement before callers get MoH, while the call goes to queue members, if any, and then onto Ring Groups.

I repeatedly have times when people complain they hear nothing when calling in.

This is what happens.

[Aug 18 10:40:59] VERBOSE[28233] logger.c: – Executing [1000@ext-queues:13] NoOp(“mISDN/2-u5362”, “CALLERID(name) is Bega Office”) in new stack
[Aug 18 10:40:59] VERBOSE[28233] logger.c: – Executing [1000@ext-queues:14] Set(“mISDN/2-u5362”, “_RGPREFIX=Queue:”) in new stack
[Aug 18 10:40:59] VERBOSE[28233] logger.c: – Executing [1000@ext-queues:15] Set(“mISDN/2-u5362”, “CALLERID(name)=Queue:Bega Office”) in new stack
[Aug 18 10:40:59] VERBOSE[28233] logger.c: – Executing [1000@ext-queues:16] Set(“mISDN/2-u5362”, “__ALERT_INFO=Alert-Info: <http://127.0.0.1/Bellcore-dr4”) in new stack
[Aug 18 10:40:59] VERBOSE[28233] logger.c: – Executing [1000@ext-queues:17] Set(“mISDN/2-u5362”, “MONITOR_FILENAME=/var/spool/asterisk/monitor/q1000-20080818-104059-1219020059.8795”) in new stack
[Aug 18 10:40:59] VERBOSE[28233] logger.c: – Executing [1000@ext-queues:18] Playback(“mISDN/2-u5362”, “custom/queuegreet”) in new stack
[Aug 18 10:40:59] VERBOSE[28233] logger.c: – <mISDN/2-u5362> Playing ‘custom/queuegreet’ (language ‘au’)

Asterisk says that the file is being played back, but there is nothing at all!

I can wait 5 minutes and then it works fine, and will be fine for ages, then just go blank again for no apparent reason.

I have had to change the setup so that callers just here ringing until the call is answered due to this problem.

Any help is greatly appreciated.

Just to add to that, I have checked the usual things like ztdummy are loaded etc also. I know that I have to have that loaded as I don’t have a zaptel card.