ICON error logs aren't really written for techs to use in the field. Even tech support will ask you to send in copies so one of the engineers can look at them. That said, the first thing I might try is resetting/reseating the MBU, checking the network connection of the MBU and taking a look at the network switch(es) the affected phones are connected to. A failing switch port can cause similar symptoms.

Sometimes the thoughts in my head get so bored, they go for a stroll through my mouth. This is rarely a good thing.