I usually plan my routes a bit before I run, so I'm aware of what streets I am supposed to be running.

I've discovered a street that wasn't mapped at all on OSM (Tanglewood Heights, Malvern), I've discovered a gated community with no public access that were marked as public (Danebury Park, Malvern), and there was another parking lot/street I couldn't access because it was behind gates.

I update the details on OSM, and then CityStrides updates their data sometime later.