Character mistake: Columbo explains to Hayward (the killer) how the accepted version of events is impossible, because when he was shot Harry Stone was standing in a dark garage and the killer could not have angled the headlights of his car in such a way that he was made visible (in order to be shot). But neither he nor Hayward even consider the possibility that the killer could have been carrying a torch, which would not only have illuminated the scene, it would have dazzled the victim and hidden the shooter.
Factual error: Columbo parks across the street from a house where a murder has occurred. The address is given as 1278 Fairfax Drive. Columbo investigates and returns to his car. A house number, 400, is painted on the curb. The house across the street from 1278 would have an odd number, probably 1277 or 1279. It would not be 400.
Character mistake: Adrian Carsini, a wine connoisseur and winery manager, pours two glasses of wine, one for himself and one for Lieutenant Columbo. Each man puts his hand around the top of his glass and begins to drink. A true wine connoisseur never touches the top of the glass. He holds the glass by the stem so the warmth of his hand does not affect the taste of the wine.
Plot hole: Dr Kepple is finally caught when he rushes to the hiding place of the calibration converter that he hid in the lamp after the murder. Why is it still there? It was a great hiding place initially when the police were searching people and the building in the hours after the murder but Kepple had plenty of opportunities after that to get rid of it. It is the only piece of evidence linking him to the crime and it is in his office so you would think that his main priority would be to dispose of it as soon as possible.
Plot hole: Carsini has a wine vault (with very expensive wine in it) with an integrated air conditioner. There are indeed wine vaults like that. But mostly active cooling wine vault are used by "amateur" wine lovers (who can't afford an underground cellar) but not by wine connoisseurs like Carsini. Active coolings are not very reliable. A power failure or a simple malfunction and Carsini would lose all of his expansive wines he collected for many years (like we saw in the episode). So why shouldn't a huge wine connoisseur build a cellar, surrounded by cooling soil where temperatures never rise that high? He is rich, he as a big estate, a villa, and he knows better to store the jewels of his passion adequately. Why store wines in a potential oven where high temperatures (without air conditioning) can even kill a man (his brother) in the first place? It is a far fetched and an unnecessary gambling just to have a murder-plot.
Plot hole: When Columbo tries to explain the position of the cars and the angle of the shot, he gets to the version when they come to the conclusion that if the car behind the other car park one way than the first car wouldn't block the light, so the shooter could see the victim. Colombo says it is possible, but in that case it wouldn't explain the angle of the shot. However there could have been 2 shooters which would instantly answers the question, and Columbo wouldn't come to the conclusion that it was a mistaken identity case. (00:43:00)
Character mistake: Columbo drives to a car lot to question salesman Charlie Shoup. Admiring Columbo's Peugeot, the salesman says, "We don't see many of these. What's it got on it? 20,000 miles? 30,000?" When Columbo tells him "100,000," he replies, "Well, I don't care what's on the speedometer." He meant to say "odometer."
Factual error: Near the end of the episode, Jackie Cooper fires a bullet into his hotel room from the balcony using a revolver fitted with a silencer. Hayward also uses a revolver with a silencer to kill Stone. This is a classic Hollywood error, as silencers do not work on revolvers (unless noticeably modified), due to the gap between the barrel and the cylinder. They also don't make gunshots nearly as quiet as shown.
Continuity mistake: During his poolside talk with Nelson Hayward, Columbo carries a large cardboard box under one arm. His coat tail is hanging straight at his side in the master shot, but when it cuts to another angle, the coat is draped over more than half of the box. (01:15:00)
Audio problem: Pay phones always dropped your coin into an internal cash box when you finished your call. In the bar, Columbo makes two calls, and after the first, we hear the coin drop as it should. When he finishes the second call, we should hear that coin fall, too, but it doesn't. (00:34:05)