The hottest ticket at this year’s Edinburgh Fringe Festival is a new stage adaptation of Ken Kesey’s One Flew Over the Cuckoo’s Nest. The show is already set to move to London’s West End once the Fringe run is over. But the production has been in trouble from the start: director Guy Masterson quit three weeks into rehearsals, headliner Christian Slater came down with a nasty case of chicken pox, and opening night has already been delayed.