Conferences are not used in Vicidial, but VICIDIAL Conferences (look at the top menu) are used. Only for calls that transfer to an agent (Remote or Live). So running out of Vicidial Conferences would limit your live connected calls to agents.
if one campaign is transfering to live agents and the other campaign is transferring to Remote Agents, that's enough of a difference in and of itself to have Very Different Results.
I would probably look at call quality and test listening to a few of those calls (record all calls for a while). I get the impression that this isn't about agents talking to someone and being accidentally disconnected: What you describe sounds like you're calling people and they are hanging up. Nobody on the agent side of the call? Do you call people and then when they answer, they hear RINGING as you try to connect them to an agent? That would definitly cause Everyone I know to Hang Up.