IMHO, the worst direction problem is when it calculates that you need a left turn at an intersection when in reality that address is to the right. More an algorithmic error than a GPS one. When the NAV is wrong, the reason varies.
Worst data problem: storing street names as (for example) xxxxx ST in some cases, and STREET in others.
Not always worth relying on, but usually worth consulting...
Worst data problem: storing street names as (for example) xxxxx ST in some cases, and STREET in others.
Not always worth relying on, but usually worth consulting...