But Dick, we haven't ...
... eliminated all the possible explanations.
We are rightly concerned when a pilot dozes off without warning, but when an ADIRU goes into dozing mode it is a non-critical rare event?
In my experience, when a computer goes into doze mode and has to be rebooted, either the hardware failed, something in the software did other than what the programmer intended, or the system design failed to take into account all the possible consequences of all the programmers' different intentions.
Hardware faults caused by cosmic rays should happen at a statistically predictable rate depending on known parameters.
Dozing faults can be caused by software. For example, a process may end up in a tight loop (unintended) or when memory is tight, several processes may end up waiting (intended) for other processes to release memory - and they don't release it (also possibly intended). This type of fault is statistically more likely on computers that run for longer than average between reboots.
If something like dozing can happen, how can we be sure enough that something else other than what is intended will not happen?