Ice grenade issue
In the Riddler's puzzle where Batman is locked in a small room and the pipes start up (subway maintenance area, I think), I have been unable to ice the pipes. It's not a matter of missing - I throw the grenade after the targeting reticule comes up, they land on the vent, make the freezing sound, but steam continues to flow out. I have tried leaving the area and coming back, and exiting and loading back into the game, but there's no change. I have still been able to ice pipes up in other areas, it seems to only be these six pipes that can't be stopped up.