I am in a group in Sydney that uses 4 of these. We experence the same issue. We ended up fitting a timer that turns the power on/off. We set the time to do this every Tue at 2AM. If they happen to go off air during the week then the timer will revive them on Tues at 2AM. Yes, its an annnnoying porblem but the timer does work as a good work around. We are suspicious of RF getting into them that causes the hang up to occur. Seems to occur in the 2-3 month time period but we can see no pattern to it.
Allen and Byron at Byonics are aware of the issue.
This is the timer we use:
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Compton
VK2HRX
Sydney, Australia
Compton