from my own testing it appears the animation keyframes for the first two spoiler positions of the lever in the cockpit are back to front.
i.e.
fully forward and down = armed (should be locked/off)
fully forward and up = locked/off (should be armed)
I found this out because when you first load the aircraft the lever is in the fully forward and up position, and when you put it in the fully forward and down position then fast taxi when you reduce the throttles back to idle they will deploy.
since I found this out they have been deploying on landing fine all be it in the wrong lever position.