DAHDI "Unable to set audio mode" warnings

I have a box connected to PABX through an E1 trunk and some clients complained abount not being able to receive calls. Checking asterisk log I see several of these lines:

/var/log/asterisk/full.5:[Mar 22 18:03:24] WARNING[18560] chan_dahdi.c: Unable to set audio mode on 20: Invalid argument /var/log/asterisk/full.5:[Mar 22 18:03:57] WARNING[13183] chan_dahdi.c: Unable to set audio mode on channel 20 to 1: Invalid argument /var/log/asterisk/full.5:[Mar 22 18:03:57] WARNING[13183] chan_dahdi.c: Unable to set audio mode on 20: Invalid argument /var/log/asterisk/full.5:[Mar 22 18:03:57] WARNING[13183] chan_dahdi.c: Unable to set law on channel 20 to default: Invalid argument /var/log/asterisk/full.5:[Mar 22 18:03:57] WARNING[13183] chan_dahdi.c: Unable to set audio mode on channel 20 to 0: Invalid argument /var/log/asterisk/full.5:[Mar 22 18:20:08] WARNING[18560] chan_dahdi.c: Unable to set audio mode on channel 20 to 1: Invalid argument /var/log/asterisk/full.5:[Mar 22 18:20:08] WARNING[18560] chan_dahdi.c: Unable to set audio mode on 20: Invalid argument /var/log/asterisk/full.5:[Mar 22 18:21:02] WARNING[27966] chan_dahdi.c: Unable to set audio mode on channel 20 to 1: Invalid argument /var/log/asterisk/full.5:[Mar 22 18:21:02] WARNING[27966] chan_dahdi.c: Unable to set audio mode on 20: Invalid argument /var/log/asterisk/full.5:[Mar 22 18:21:02] WARNING[27966] chan_dahdi.c: Unable to set law on channel 20 to default: Invalid argument /var/log/asterisk/full.5:[Mar 22 18:21:02] WARNING[27966] chan_dahdi.c: Unable to set audio mode on channel 20 to 0: Invalid argument

Restarting the system seems to get rid of the warnings and the problem for a few days and the lines do not appear when the system is working normally. Anyone know what could be causing this?

System data:
Asterisk 1.6.0.26
Dahdi 2.3.0.1
Libpri 1.4.10.2

Thanks!

There are several places in the code where that could happen. Unfortunately, Asterisk 1.6.0 is no longer supported. See (wiki.asterisk.org/wiki/display/ … k+Versions). Can you reproduce the problem on Asterisk 1.8?