My 2016 Navigation system has started getting lost...

Wondering if anyone has some hints?

Sometimes it'll catch (I assume) a good GPS location when I start the car, then get progressively more lost as I drive depending on how many turns I make.

I have a set of factory cross-bars on the roof and now a bike rack on it. Could that metal be interfering with the GPS?

I did have a stubby antenna, but recently switched back to the stock one to rule that out.

 

Seems to be getting worse...

I tried disconnecting the battery to maybe reset an algorithm to learn the tire rolling circumference and that seemed to help for a bit, but now the map is off in the weeds again.

Some googling seems to suggest a new antenna base might fix it? Any experience here?

 

Anybody know how to force the system to relearn the tire size? The Navi still things I'm not driving as far as I really am and loses it's mind if I drive straight for too long.

My Ford Tourneo Connect that I drove in Germany had to relearn with winter/summer tire swaps and I could do it by disconnecting the battery for 10 minutes....