We know that Bert Convy blew some puzzles on SP by accidentally blurting the solution, and Tom Kennedy blew a puzzle on PW+ on today's show.
Allen Ludden had mentioned on the air that he had accidentally blown a couple puzxles, but were any of these blunders actually aired? I don't recall ever seeing him do that. I would imagine he'd insist on editing out any embarassing mistakes like that. While I've never seen him blow a puzzle, I do remember a funny moment when the password was SHORE, and Allen turns to Elaine Joyce and says "Ok, Dinah... uh, Elaine" and then there was an obvious edit with Allen saying "Ok, we'll put SHORE on the board because Ludden has a big mouth!"