ACD Calls going to 2 agents at same time

[lmtb]

Over the last 5 days we've developed an issue which appears to be localised to one Trunk Group.
At certain points in the day, we're getting 2 agents presented with the same ACD call, they can both pick the call up and can hear/speak as normal, only difference is there's now 3 people on the call - both of the Agents and the Caller.
Different agents each time, not the same VDN or Skill either.
No hardware changes been made, so far as I know there's been no firmware upgrades either.
Agents are using 4610 phonesets.
Trying to track a call live but in the meantime, just wondering if anyone has had anything similar and can suggest where to start looking.
It's a fairly old PBX CM4, multiple other Trunk Groups programmed and working with ACD routing, without any reports of similar issues.
Any clues?

 

[kyle555]

Any analog trunks in the mix that might be crossed? Your scenario is sort of impossible in the context of the PBX causing that mixup - not to say the "2 agents, 1 caller" isn't coming from somewhere else. If it happens at all predictably to a certain person, or dept, put a trk-id key on some of those 4610s and find out if it follows a particular trunk group/member

 

[lmtb]

Thanks Kyle555,
I agree, it's something an ACD simply shouldn't be able to do. I was sceptical until I played the calls back from the call recording system, and sure enough we have a regular ACD call coming through to two agents at the same time !! Can't say it's happening to one particular user, skill or VDN, only thing I can find as common ground is the E1 that the calls are arriving on. We've got no analogue trunks in play here, guess I'm just going to have to go down the MST trace route with Avaya and get them to analyse what's going wrong when it happens.
Thanks again.