Also something that could be an issue, but as far as I see a lot less problematic than spirits.
At least with drones you can avoid their sensors, try to evade them, shake them, jam signals and you have some means to defend or attack against them. They also either need to be controlled or are quite limited with their dog brains, not capable of much more than direct engagement.
But once a spirit finds you it can track you astrally, moving at the speed of thought, through walls, floors or ceilings, so you'll never lose it. And then it'll suddenly appear 500m above and behind you and hit you with a LOS spell or power. They're also far more intelligent than drones, capable of understanding what their advantages are over mundane creatures and make full use of them.