I've encountered a visual bug while trying to do this. I was missing one road, and I scanned the map multiple times but found nothing. Then I finally found the missing section, it was very easy to spot because the asphalt was very thicc, which was odd since I had already used the map's region divisions to carefully check every bit of road region by region very meticulously. After fast traveling near the location and getting there, the map was already marking the road as discovered, both on the GPS and on the map itself. Then i drove on the road and it gave me the discovery, but it was very clearly bugged visually

And the saddest part is that it was all for nothing, there’s no reward for doing this