I recently found several cases where a street is broken or split, even though it is continuous in real life. This causes problems where using navigation programs, as the navigation program makes a route to avoid the break, even though it could route straight through. An example is here: Map 17/40.79526/-74.46899. Morris Avenue changes its name to Morris Street, but it is the same road. However, the map incorrectly shows that they do not connect. Why is this?
There were many other tags here that I am not familiar with as I live in a different country, so others can verify that this was the cause.
For the other cases, open in an editor and zoom in close where you expect there to be a problem and check the tags. Also ensure the sections are joined and don’t have a small gap between the sections which could be a mapping error that stops routing.
You also need to be familiar with the area as there may be a barrier or block or gap in the way that is designed to stop traffic from routing through that point.