Our CME has an 800 number being forwarded to it that rings to a hunt group.
At least once a day the number will be busy. The only thing I do to fix the problem is to restart the CME.
I have done an ISDN Q931 debug and I do see the calls terminating on the PBX, but the PBX is not sending them to the hunt group, just getting a busy signal. All other DIDs inbound and outbound work fine.
I apologize but I did not save a copy of the debug. I'll add it next time it occurs.