I have a BCM 400 4.0 and when I make a conference call, all works fine until I bring in a third party. Once I do that, all calls get condensed to one intercom line, so when I try to drop one person, I can't. Is there a way to make this not happen this way? I have 3 intercom buttons, and even if I bumped it up to 4 it did not help. Thanks,