i have a half dozen pics on my phone of the exact same thing, putting me off into a mall or a park next to where i live (almost every time with the park...a good test of the system) when Im driving next to them.
Question for you. Do you keep an iPhone plugged into the usb port in your car?
I normally do (iPhone 5), and also have it connected via blue tooth, esp on longer rides. however, after forgetting my iPhone cable last week on a 5 hour drive, i grabbed one of these 5 buck cords at my first gas stop ( i was towing a loaded haul..turns out this thing can suck the gas down like a truck when towing like one ) and this cheap cable quickly failed, so for the next few hours i was driving with my phone just connected via bluetooth. Gps was set for my destination, and to my supprise, it got me right where i was going with no errors, missed tracking etc.
ok, a fluke perhaps. However the next day, when i had to go right to the end of the city to drop off the trailer, again, no phone plugged in, it got me there and back home(almost 40km round trip), with no issues again.
by this point I'm starting to suspect my phone is the issue. next day, i set the nav again for a 30 odd km return trip through the city to a place i know how to get to, watching the screen when i can, and the thing seems deadly accurate.
there are only 3 things different from when i was having all my problems previously. no phone plugged in, dry roads (no ice etc) and above 0 temps.
I know tire size/winter tires have been a key suspect in a lot of nav problems, but this would seem to suggest otherwise.
I should have kept my summers off longer to really look into this, but yesterday i put my summers back on, so today i am going to re-do the my destination from two days ago, but with my phone plugged in, and with any luck, it will mess up again and give some real idea as to the problem.
i do know one thing, its been nice having a working nav for the last week or so.