I had a similar issue with the Volvo I had before my Jag XF.
The Volvo dealer ended up replacing the Nav "antenna" inside the shark fin, NO FIX, replaced the antenna cable between the antenna & the unit, NO FIX, replaced the player/unit that holds the disc, NO FIX, replaced the computer control unit in the rear fender (for the NAV unit) FIXED.

FYI, Mine would follow my route, if I turned right it turned right, if I went 5 miles north, it went 5 miles north and so on, It was just not my true location....at one point when I was at the dealer, I had me about 40-50miles away, in the middle of a lake, BUT it showed me driving though the lake perfectly as if it was on the actual roads around the dealership.

Question, Did you recently have the battery replaced.....that's when all my issues in the Volvo appeared. It seems that the slight spike in electrical system from a dead (disconnected) battery to a NEW battery fried the computer control unit.

Good luck.

 

A couple of months back an XK coupe was here with that complaint. At first I couldn't substantiate it, then after a couple of drives the NAV put the car at the Indiana/Ohio state line while I was driving around Indianapolis. The trouble was two-fold; Nav antenna AND antenna coax lead to the NAV DVD reader. The tiny coax connectors are extremely delicate. Interrogation with the Jaguar SDD diagnostic equipment confirmed it by logging a fault for the NAV antenna.

I'd suggest finding your friendly dealer and let them investigate.

Good luck!