The button on the lockdown bar can't control the ramp diverter. With the fast flow of the ramp shots, it would be too hard to move your hand quickly from the flippers to the fire button repeatedly. Just my opinion. It must be for something else, like the crossbow shot.
I'm most intrigued with the area between the speakers. Could that be a camera? Or maybe red/orange/yellow light that shines on the player when Smaug breathe fire?