When Ada explains how she killed the operatives in the central command station, a security-tape replay shows Ada standing in the center of the room shooting outwards. But when Alice first enters the room, there are glass walls in front of each workstation, with blood splatters on the inside.
This would imply that the workers were shot from behind. If Ada had shot from the center of the room, the glass walls would have been shattered.
During the fight between Alice and the Tokyo zombies in the well lit, white hallway, Alice shoots and smashes the zombies, with blood shown coming from the impacts. However no blood ever appears on the white walls until the end, when only pools can be seen on the floor.
When the system has to reboot, a drawer opens revealing Alice's clothing for the rest of the film. When Alice walks into the hallway her shoes are a high wedge heel, while later in the film during combat scenes, Alice's heels change from high wedges to low wedged heels.
During the attack on the Arcadia, Alice is seen shooting quarters from her 12 gauge shotgun through the windshield of one of the tilt-rotor aircraft, killing the pilot. However, the diameter of a quarter is 0.955 inches; therefore, it would not fit in a 12 gauge shotgun, as the diameter of the shotgun barrel is only 0.729 inches. In addition, not only would a projectile such as this never penetrate an armored windshield as is found on tilt-rotor aircraft, the glass "spider-webs" with high energy impacts due to layered plastic laminates, and doesn't shatter, like plate glass would.
In the Moscow car chase a Las Plagas zombie is shooting at the heroes car with a DShK 12.7mm heavy machine gun. The bullets bounce off the car's trunk, while in reality they would go through killing the passengers.