Anything where you don't hit the target is a miss so yes. Non-exhaustively and off the top of my head; running out of battery, electrical fault, losing signal/break in the fibre optic cable, shot down and operator error are all potential causes of a miss.
No, they miss a lot. ~5:1. But that still makes them cheaper than artillery rounds and they do a lot of damage and can do both recon and the subsequent attack with the same package, and without delay.
Hmm, I didn't realize. Do you mean ~5:1 is better than the miss ratio of artillery rounds, which makes them cheaper? Because I think a small FPV drone is about US$600 and an artillery round is about US$800, but that isn't a fact caused by the miss ratio.
TBF based on Ukraines own statistics drones miss a lot as well.