Export the logs to an excel file from the web interface, and then go back to the time of the instance, if you see a ton of phones disconnecting and reconnecting for no reason, it is likely a network issue... Mitel 3300 doesn't have any issues with this, so it my expectation is that the case. You might have to do some wireshark traces on a mirror port of the 3300 uplink port, they get huge fast, but might be more useful in finding the issue. When this occurs, look for large numbers of broadcasts just before it, there is could be a port loop somewhere.