I have a BCM 400 3.7 with Call Center. 14 agents with headsets. All of the agents are having volume issues intermittantly. They all have M12 with new batteries. some times they can hear just fine then the next call they can't hear anything, unless they pick up the handset then the call is clear. Any suggestions. I am thinking maybe put power supplies on the M12's instead of batteries. This probelm is only happening to people with Headsets....