Here is a pretty detailed explanation of the Yeti's problem (From MiceChat):
"Multiple sources have confirmed that Disney's Imagineers have a VERY serious problem on their hands regarding the infamous "Disco Yeti". Expedition Everest enthusiasts have known for some time that the complex animatronic has been parked in B-Mode and Disney does not appear to be in any hurry to return the figure into its fully functional state. The concrete and steel foundation supporting the Yeti may be cracked and the repairs required will result a prolonged closure of the attraction.
If waiting until a scheduled refurbishment to repair the Yeti's foundation were the only obstacle facing Disney, then Expedition Everest fans' impatience would be tempered with the knowledge that the Yeti will eventually be fixed. But the real obstacle may be insurmountable.
You see, the Imagineers designed Expedition Everest as three separate and independent structures. First, the mountain itself. Second, the roller coaster track and track supports. Third, the foundation, support beams, and animatronic skeleton of the Yeti itself. Construction of all three structures was so complex that Disney had to rely upon a 4D software modeling program known as ConstructSim (a product of Bentley Systems, Inc) to help them coordinate the complex construction timeframe and coordination schedules.
There are rumors that a serious mistake in the application of ConstructSim resulted in improper staging of the Yeti foundation and support structure construction. The error in sequencing prevented adequate curing of a portion of the Yeti's foundation prior to the overlapping fabrication of mountain elements and roller coaster track. The premature construction produced additional stresses on the animatronic figure's foundation and produced excessive stress points. The mountain and roller coaster track construction, in turn, prevented the foundation from being visible to construction inspectors.
Expedition Everest was too complex in its design to allow construction without a 4D software like ConstructSim. Conversely, repair work on the Yeti's base will require selective removal of parts of the mountain structure and ride track structure. This refurbishment will also require extensive software previsualization. Disney's Imagineers must figure out what went wrong in the original construction previsualization before they can trust any future refurbishment previsualization.
A construction defect this critical in a project this complex can be a very daunting task for any organization to overcome -- even a group as talented as the Disney Imagineers. The question is -- will the Disney Corporate Bean Counters allow the Imagineers to fix the problem, or will they decide that "Disco Yeti" is "good enough"?"
http://micechat.com/forums/walt-dis...n-yeti-expedition-everest-mystery-solved.html