We've been running into some problems where specific coordinates could not be reached via findlocation. After a lot of digging and testing, I finally understand why.
I was under the impression that the FindLocation command would bring you as close to the coordinates as possible, and then connect the remainder via a temporary edge. But the way that it's done right now is the opposite: It will connect the temporary node to the nearest point along an existing edge, and then try to bring you to that connection. The problem is, this is not always the shortest route, or even a possible route.
Example screenshot:

If I'm at the lapis block and I try to navigate to the redstone block's coordinates, then that navigation will fail regardless of my distance setting. Because the redstone block will connect to the emerald line, and then the navigator concludes that navigation is impossible because the emerald line cannot be reached from the lapis line.
This is the case even when distance settings would have allowed the redstone block to connect to the lapis line directly.
I'm not sure what the most elegant solution to this problem is, or even whether a solution is desired. But this is the nature of our problem.