I have played at Nevada casinos and they change the ball during the game. There are three different along the rail, all different sizes or material. (they look different colors and I could see the size variations)

Why a casino would use only one, is beyond me.

These guys must have had some super magnets or electro-magnets to be able to stand near the wheel and effect the ball.

I'm suspicious that the way they controlled it may have included installing something to rig the wheel so that a specific group of three numbers would attract the ball. So it was always the same three number range.