I've had the opposite experience on the very few times I've tried the built-in nav. I was driving home via the M4 but it was closed due to the roadworks & the nav didn't tell me. Switched to Google Maps on Android & that correctly routed me around it. Not that I needed the nav, but I usually turn it on for exactly that purpose and to give a decent ETA, so complete fail on the part of the VW version!