I will sum up what appears to be wrong based on reports by
@Lee ,
@marni1971 and from a lunch with an imagineer report by
@RedDad ...guys feel free to correct me if I slip up.
The problem was an improperly designed shoulder joint on the Yeti that was discovered in the 11th hour. The engineers decided that in increased maintenance schedule would correct the problem. Either the increased maintenance was not done of that did not fix the issue...the story seems to differ deepening on if WDI or operations is telling it.
This is where the fixed stalled. Who gets the bill...WDI or Operations.
It is also been reported that changes in regulations regarding moving items over guests heads has changed since the problem occurred making replacing the yeti and returning it to full operation no longer legal.