The nav is horrendous. I regularly go to the airport. Enter Melbourne Airport and it routes you around the back of the airport and directs you onto the runway....
I went up to the dandenongs from the eastern suburbs. It picked an interesting path and I assumed it was one of the lessor known roads. Found out it wanted me to go up a fire track...
From the dandenongs I wanted to go to a local picnic spot. It directed me down a steep road where signs said it was a dead end and last chance to turn around. Got to the end and there was a creek with the next road on the other side of the creek. Zoomed in on the nav and you could see that the road ended, and then the creek. Yet the nav plotted the blue line directly across the creek as if it didn't exist. Maybe it expects you to jump it....
The estimated times on the nav are always ideal times. If I plot a path to my work from home during the morning peak then it'll still say 25 mins, even though at peak it is an hour.
At the end of the day it's easier just to use google maps or waze on your phone. Eventually it'll get patched in an update but for now it is better left alone.