Well, long story short, when the ride went into action, Disney’s engineers quickly discovered that the numbers weren’t adding up: the internal stresses the ride was producing every time they turned the animatronic yeti on were literally tearing the whole mountain apart. That precision in timing is actually kinda critical, because if certain parts of the structure are subject to stress too early (e.g., before the concrete is fully cured, before additional supports have been installed, etc.), they’ll be permanently weakened. TL/DR version: the structural layout of the Expedition Everest attraction is so complicated that Disney had to use a technique called “previsualisaton” to construct it - essentially a four-dimensional blueprint that specifies not only how the structure should be put together, but the exact point in time that each step should occur. The really hilarious part is that the busted Yeti is even worse than this description makes it sound.
