Probably a completely different problem, but my system also
crashed last night, and my router crashed as well. In fact
I suspect the router crash took down my system. The last
thing in the log was a message I've never seen before
about networkd service watchdog timeout. (didn't appear
in any of the old logs still on the system).
I'd hate to think a bad router could crash the system
but it sure looks like what happened :-(.