Multiples FACETIMES sessions

We have created multiple FaceTime sessions to place multiple video-calls to remote Apple FaceTime subscriber. We have noticed that if one remote subscriber terminated a video-call, 28 to 30 seconds (it shows a reconnecting messahe) after, all the other sessions are killed.

We have also noticed that creating multiple Facetime Audio session, the problems is not present.

We are using a iMAC with Yosemtime 10.10.3

Is there any way to fix this situation?