FXO line taking a long time to initiate ringing



I am using 3 of my 4 FXO ports on our UCM6204 to control come analog call boxes (gate controls). Basically I have it to where a person hits the call button on the call box, it acts like an incoming call and triggers ringing an extension. The problem is, from the time the button is pressed to when the extension is actually rang, it can take 20 seconds or more. On the status page I can see the FXO line active, but in the Active Calls section, there’s nothing happening for a good 20 or so seconds. Why is this happen and which of the 1 trillion settings on this PBX is the culprit?