DE410E hardware Echo Canceller stops working

We use our machine as a SIP gateway to bridge calls from a SIP Provider to a Call Center PBX (inbound and outbound).
We started out with a D410E (without the echo cancel module) and then purchased the EC100-128 separately to help deal with echo problems.
I followed the instructions at http://wiki.openvox.cn/index.php/OpenVox_DE410E_Asterisk_1.8_Dahdi_en

The Problem:
The hardware echo canceller works great at first but after 15 to 20 minutes, many of our outbound calls start getting echo. These are calls going from our PBX to Asterisk to our SIP Provider. Inbound calls seem unaffected. In testing specific lines, I find that specific lines appear to still be getting echo cancellation on outbound but many are not. Restarting the Asterisk and Dahdi service will fix the problem but after another 15 to 20 minutes it starts happening again.

Suppose you are using DAHDI 2.4, could you try to modify the base.c located in wct4xxp directory, add

#define PEDANTIC_OCTASIC_CHECKING

at the first line

and then make install

I've recompiled with the change you suggested. Not 100% sure what that does but /var/log/syslog does not show anything from wct4xxp when we begin to experience the echos. Specifically: "Yah,read (or write) can be slow" nor "Read (or Write) timed out!" are not popping up in the syslog file. Is there anything specific I should look for?

Correction and clarification on problem:
The echo is actually occurring just over 1 hour after restarting asterisk and dahdi services (not 15 - 20 minutes). And again, the echo is on an outbound call from PRI -> Asterisk -> SIP. The echo is heard by the person we are calling.

Hi,
Could you please add my MSN/G-talk:[email protected] or tell me your email?
I want to test with you.

I sent you an email Jessie.

I found something on another thread:
www.openvox.cn/bbs/viewthread.php?tid=1493&extra=&page=1

The symptoms described are similar to ours with the only difference being they are using a single span and we a quad span.

I am wondering if the firmware upgrade you mention would also apply to the DE410E? And is it available?

I have also heard of race condition causing hardware AEC to not function correctly in different versions (2.2 and up). Therefore, I have decided to take a different approach and use a software echo cancellation. You should pick the right software based on your echo tail (delay). In my case, echo tail was usually around 150ms so I have decided to use the PBXMate.