I didn't read through every post, so I don't know if someone mentioned it, but it seems some people think the Yeti itself is broken and that's not the case.
Taken From: The World according to Jack on allears.net
"I mentioned earlier that the yeti stands on his own foundation. In addition to this, the track and mountains also stand on their own, separate foundations and do not touch one another. The designers endeavored to put six inches of space between the track and the mountain. This was necessary to insure that the vibration of the trains rumbling through the mountain and the swaying of the track did not shake, crack, and damage the mountain’s structure. Unfortunately, the yeti’s intense movement proved to be too much for its foundation and it cracked sometime ago. Because of this, the yeti has been switched from Mode “A” operation (movement) to Mode “B” operation (stationary with strobe lights and fans). It’s my understanding that the damage is great enough that repairs will need to wait until the attraction is closed for rehab."