Can make and recieve calls but sometimes get a fast busy

[PhoneTeck]

We have a System: G3csiV6 Software Version: G3V6i.03.2.239.7

My problem can best be explained in the picture, are building can receive calls and make calls but sometimes we get a fast busy. I have called the phone company and they tested the circuit and they say everything is fine with the circuit. I used hardware manager and the system doesn't show any errors or alarms. I'm at a cross roads as to what I need to do next. Any help would be appreciated.

 

[PhoneTeck]

Sorry don't know why the image isn't showing up, here's a link.

https://www.dropbox.com/s/znnpnnl2e344yxf/trunk.png

 

[offdahook]

I would you change ds1 board and/or ds1 cable, also check the back plane on the switch. If still a problem have the phone company come out and verify good at the mux/dmarc.

what are the reults of "list meas ds1 l 01a04"?
what are the results of testing this same board also?

may I also ask how is it that the trunk group and ds1 board ports are not aligning..i.e tg 16/01 corresponds with 01a0405?

 

[PhoneTeck]

I yesterday replaced all the cards in the Pbx one by one and also tried another csu/dsu connecting with a cat 5 cable. The problem still exists. At&t has been out twice and they say everything is working fine. Is there anything else I can try?