The message queue for the respective task is full due to simultaneous events generated by several devices. This could affect Z-Wave, Zigbee or LAN devices. Addressing the problem with devices that are going haywire is the only way to prevent this to happen again. You will need to power cycle the hub to clear the locked queue, though.
There's only so much multi-tasking / multi-threadedness that can happen before we reach a point where parts of the system need to say.... Right, let's record these things in some kind of sequence of events... Says the data guy who has to often deal with the way things are recorded... Maybe this is more about me than the actual problem
I guess my concern here is not knowing that happened. I tend to check my logs fairly often, but not every day. And this being a friends I may not check his logs for several weeks. And in this case the devices wouldn't normally show up doing anything until they were needed and then it would be too late. For instance the siren wouldn't go off unless his alarm tripped. And then it wouldn't go off.
Then, in the end I expect you need to deal with the situation at hand for your friend, either follow through on finding an explanation / solution through HE platform corrections and/or some form of monitoring to detect the situation occurring again. More likely you should implement both.
Is there a way to monitor or detect when an error is logged? I have the means to get notifications from his hub. Just don't know how to detect an error.