These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
On one episode, security guard Jeff Addis dialed the last digit into the locked safe containing all of the $100,000 Mystery Tunes, however when he tried to open the safe it wouldn't budge.
Tom Kennedy (realizing what happened): He forgot the combination!
One episode had two incidents within just Melody Roulette; firstly, a $500 tune is suddenly worth $500,000. Then, in a more infamous blooper, a player correctly guessing "Please Help Me I'm Falling" ... ends up doing just that.
They Changed It, Now It Sucks: In 1978, during the disco craze, the show decided to adapt to the times, with a new set, a group named Dan Sawyer and The Sound Machine, new vocalists (Kathie Lee had left at this point), and replacing Tommy Oliver with Stan Worth. Unfortunately, they also decided to cheapen the show (though not at first). Ditching the Mystery Tune, turning the Golden Medley into the Golden Medley Showdown (adapting a tournament format used for Mystery Tune losers the previous season), and in 1979, lowering the non-tournament budget from $15,000-$20,000 to $6,000-$7,000 (the most jarring example being replacing the CAR space on the Melody Roulette wheel with a lesser prize package). NTT lasted three more years, but some would say it wasn't as good as the Mystery Tune days.
This would also apply to the Lange version, produced by Sandy Frank himself. While the Golden Medley returned to its 7-in-30sec format, with monthly tournaments held for those who got the 7, the overall budget remained on par with the later Kennedy years; the $100,000 prize was a prize package including $10,000 cash and a Pontiac Fiero. The potential Melody Roulette top prize, previously $6,000 (or $4,000 & a car/prize package) decreased to $4,000 (or $2,000 when it adapted a one-spin format midway through the season). Finally, each GM tune paid $250 in prizes instead of $500, and all 7 won a vacation instead of a car.