Navigation quirks

My navagation system has had several recent odd directions. One, repeated several times, has my getting off the correct exit, then going past my destination by 10 - 15 miles, then turning around and going back to the destination. No big deal if I see my destination, but I am always showing 20 to 30 miles farther to go than actual. Another, I input a (small) city with no address as my destination and the nav took us on an "adventure" of about 20 miles of single lane dirt roads then dropped us at our "destination" which was actually about 10 miles from the city (the city showed clear as day on my nav maps). Finally, I entered an address that others travelling to the same location told me produced screwy results in their garmins etc. and in my Prius just plain froze the system until I powered down and back up. BTW, none of these locations involved roads built after I purchased my 2006.