I, Robot (2004)
Spooner gives chase and when he arrives in the lobby below - we see Spooner holding the large gun and subsequently holstering it back in his shoulder holster before picking up the gun Sunny had dropped while fleeing - which is also a large gun.
Errors in geography
Incorrectly regarded as goofs
However, we do not see the array of robots until after Spooner and Calvin arrive, so it is possible that one or more robots had to move, but this was not shown on screen.