The drones have machine guns, yet they never seen to hit the heroes, even when the heroes are standing still (this is an very common depiction in action films).
A few times, Tallis uses his grenade launcher to blow entry holes --at very close range. In reality, the exploding shrapnel being that close would kill him.
Towards the end of the movie, three red drones are hunting Tallis in a sewer. The water level is only knee deep. Tallis dives under the water's surface and the shot shows him swimming in water that is waist deep to the drones. The next shot shows Tallis coming up out of the water behind the last drone and killing it. However the water level is only knee deep. Tallis then ducks back under the water and we see a shot of him swimming around again in water that is at least waist deep.
When Tallis and the girl jump out of the window, and Tallis blows a hole in the street so they can fall into the sewer. There is a shot from under the water that shows them hitting the water and then swimming back up to the surface, but the next shot shows them stand up and the water level in the sewer is only knee deep.
Before the end fight, the super drone shoots Tallis' gun away, which is lying on the ground. The rope which is used to pull the gun away is visible.
Reflection of a crew member seen across the street from Tallis as he steps out from behind a building after shooting the rabbit.