Actually, I have noticed that in some cities, the police seem to decide to stop doing their jobs. I will plop a police station and it will work great for something like two game days, then the police disappear and the drones stop going out to catch criminals. If I destroy the station and rebuild, it will work again for like two game days. If I add more vehicles, they will work for....get this....TWO GAME DAYS!!!! It is frustrating. So, I have your problem too.....