External Call Forward not wworking

[almostretired]

I have an MICS customer running 4.1XC WI6.15 and PRI. If a call comes in on his DID while his set is forwarded, there is a 4 or 5 second delay and then an "all trunks busy". I have verified there are lots of free channels on the PRI and tried just an internal extension to extension call which transferred out no problem. I've also found that outside calls answered by reception will also call forward properly when transferred to his ext.
I've tried removing Outgoing Name and also CLID with no change. Originally the DID was programmed as Ring Only bringing it in on an intercom key. I've tried making it Appear & Ring which did not clear the problem.
Has anybody out there encountered a similar problem?

Any help is appreciated.

 

[bwtc]

The only advise that I can give is to upgrade to at least 6.1MR3. All prior versions have PRI issues.

 

[cook1082]

I have this on a BCM 3.6.But it's not the BCM it's the dinamic PRI from the CO.Its forwarding the calling partys CLID and the CO dosen't reconize the number.It only happens on direct external calls to the forwarded phone. The Co said if it was a so called real PRI it would work.