Randomly half-voice at sip/zap


I have a very strange question. I’m using trixbox with Asterisk

I configured and installed the HFC ISDN card with a script, as here:


Now i have 6 SIP hardphone, and softphone, using 1 SIP trunk to call
out the world, and 1 ZAP ISDN trunk to receive calls from the world.
The incoming route directed to a ring group.

Sometimes the incoming calls - from pstn - are not, the caller do not
hear any voice from us. When i call out on the sip line, it happens
indirectly, so i can’t hear nothing from the other side, especially
when i call my sip telco provider. (10 try, 2 wrong) If they’re
calling me, everything is ok!

I tried the echotest, it’s working fine!

Please help me!

Thanks in advance!