I hate to post disasters by others, but this seems like a great topic for discussion.
N's interpretation of the auction: X was penalty, 4♠ showed a lot of shape, 4NT was natural, 5♣ showed a minimum, 6♣ was a gamble necessitated by the SOM.
S's interpretation of the auction: X was takeout, 4♠ was to play, 4NT was RKC, 5c showed 1 or 4, 6♣ showed terrible (or short) spades ith ♣ support, 6NT was to avoid a ♦ ruff.
Which call after the 4♦ preempt was worst?
Benefits include:
Plus... it's free!