Well, while they could turn 'on' the Yeti's A-mode, it would pretty much eventually tear apart the foundation. Even turning on the Yeti's arm would stress the boom and the concrete base more, possibly resulting in the Yeti crashing and damaging the track if used on a regular basis. Even when the Yeti is retracted back, like he is now, he's still cantilevered out on his boom, using pneumatic power to move his arm, which weighs a lot, would be like using a lever to jiggle the whole foundation every time a train goes by.
The fix would involve immobilizing, or supporting, the elbow joint, and using pulleys to move the arm. Even so, you can see why this is risky due to the problems with the frame supporting the Yeti. It would be like trying to drive to work everyday on an emergency tire, hoping that it would hold up until you could get your car totally fixed.
The definitive fix would involve shutting down Expedition Everest for at least eight months, IMHO, while massive construction is undertaken.