Analog line has one way communication

[WCTek]

I have two 3300MXe with 8 peripheral nodes that attach 4 to each 3300. The controller A - I did not get any complaints about the 1-way communication. But controller B - the tenants complained that the 1-way communication occurs intermittent. Like this:

The phone is ringing but they can't hear anyone on the line when they answer the call. If the caller is calling back, they will be connected. It happens more and more to my tenants.

The Mitel system was installed back in June and I did not have this issue back then. It began about 4-6 weeks ago. Mitel Tech rebooted the controller B but did not resolve the issue. Do you have any idea on this issue?

I have release 8 on both 3300.

 

[MitelInMyBlood]

How many analog lines are we talking about here?

 

[WCTek]

I have 640 analog line in controller A and 550 analog lines in controller B. All of them are using ONS cards. The two controllers connect thru IP Trunk via Cisco 6500 (core switch). Each controller resides on 1 side of the building.

 

[slapin]

Is there any pattern? Like dialing external numbers or specific set of extensions? Or incoming calls from external lines? Where those lines are connected to the system? Is there any messages in system logs from E2T module? How many DSP and echo cancellation modules installed in controllers?