You have to admire the Nav lady's tenacity -- she will almost NEVER admit that SHE cannot understand what you said! Reminds me of the stereotypical driver who won't admit to being lost... and some of my colleagues.
It also took me a while to realize that some (certainly not all) of the nonsequiters arise when giving NAV commends when the Info screen is active and "car" commands when the MAP screen is active.
Also, it makes for a great entertaining game on road trips called "fishing for Easter Eggs". So far, "hungry" is the only voice one we've found, and that's well known. I wonder if there are a few more in Japanese. You can get a giggle out of the attempted responses.