Went with my parents on Sunday to visit relatives in the unfamiliar territory of Sonoma.
Setting off from Palo Alto in my father's Prius - an earlyish (2004 or so) NHW20, with fancy built-in nav system - I was in the navigator's seat, on account of being the one most likely to be able to operate the car's nav system. And, of course, I had my Magic Elf Box to fall back on.
After some poking, I managed to get the address punched in. It promptly told us to head for 101; my father, meanwhile, was making for 280. I got tired of being told to turn around, and found the "suspend navigation" button.
A few blocks later, as we headed west down Oregon Expressway, I noticed that the nav display had us several miles south, in Mountain View, near Rengstorff Avenue.
By the time we reached 280, the nav system was firmly convinced that we were in Boulder Creek, going cross-country through the redwoods in the general vicinity of 9.
I couldn't find any button for "please reassess our location and report back when you have a clue."
Somewhere around Hillsborough it came to its senses. When I noticed that the map display now matched the surroundings, I re-enabled navigation, and it worked OK the rest of the trip.
Glad I wasn't relying on it.