ok i got there with my new character. at first i couldn't get them to move no matter where i stood below. I went up to the
dials buttons at top, and got on the little 'bulb' area sticking out of the wall right in front of them and tried from there, fire... nothing... ice... they moved! woot

might try jumping on to that front piece and shooting at it, i also had to shoot slightly below the crystal to get it to move rather then directly on it.