3) If some use unicast and some use multicast, sometimes those using
multicast loose the video stream but keep the audio stream. Those using
multicast get good connectivity as per situation 1. The bridge server must
also be sending out good multicast traffic, but is having problems receiving
the traffic, as shown by the fact that the unicast clients sometimes loose
video. This could be due to any number of factors, e.g. the routers could
be set up so that multicast traffic is a low priority, or multicast could
just not be set up correctly on the routers.