Just before she accompanies Columbo and Alex into the screening room to watch the incriminating video, Janice Benedict's hair is swept up in a bun behind her head. When she enters the room, her hair is in a long ponytail.
Alex Benedict has long hair in the Maestro tradition: curling over his ears, covering his neck, flipping up in back and generally flying around in disarray. But there is a memorable (and largely irrelevant) scene where Columbo visits Benedict's home and asks how much he pays in taxes, how big the house is, etc. In this scene, John Cassavetes' hair is visibly shorter than before or afterwards; it is trimmed farther up on his ears, neatly pouf-ed all around, and shaved in back to expose his neck. The likely explanation is a bit of Columbo history: this scene likely was some of the extra footage added after the network ordered director Nicholas Colasanto to lengthen the episode, from 90 minutes to 2 hours; Cassavetes apparently got a haircut before the additional scene was shot.
When Columbo interviews Paul Rifkin, the horn player in the jazz bar, the whiskey bottle to Paul's right disappears and reappears between shots.
The position of the carnation dropped under the piano is first shown to the left of the piano leg, then under the piano not near the piano leg, then finally behind the piano leg.
When Columbo is at the garage where Alex Benedict is picking up his Jaguar, the storefronts across the street have brown doors and visible windows. After Benedict drives off, Columbo goes into the garage to talk to the mechanic, and now the storefront has been replaced by a nightclub; the doors are now black, and the windows are covered.
While leading a rehearsal of Wolfgang Amadeus Mozart's "Eine kleine Nachtmusik", Alex Benedict tells the orchestra, "Remember: quasi una fantasia." That particular musical direction does not appear anywhere in this piece. It is famously associated with Ludwig van Beethoven's "Moonlight" piano sonata.
The piece that begins the live broadcast (and opens the show) is Ludwig van Beethoven's 6th Symphony (a.k.a. the 'Pastorale'), but the orchestra starts playing it from the 4th movement, not the opening, and then some measures into it. No professional orchestra would do this.
In the same scene where Columbo tells Alex about the extra mileage on the Jag's speedometer (odometer,) he refers to Jennifer Wells' "apartment". The viewers have already seen that she lived (and died) in a single family dwelling, AKA house.
Mrs. Benedict tells Columbo the musical notation "Quasi una fantasia" means "like a fantasy" in Latin. In fact, the correct translation is "almost a fantasy," and it's Italian, not Latin.
Police detectives would not have a minor child identify a murder suspect in person putting them in danger with or without a parent present.
While Alex Benedict takes great pains not to leave fingerprints from his right hand as he climbs through the washroom window, he rests his bare left hand on the tiled wall at least twice, leaving distinct hand and fingerprints. However, this is not a Goof, as his prints would be expected inside the washroom as he used it just before leaving with his wife.
It may seem a continuity error by the fact the bird cage was uncovered when the conductor leaves the murder house, and the bird in the cage is uncovered and squawking. Then when Columbo is viewing the murder scene (and with the conductor), there is a cover over the cage. However, the bird died from the gas leak (Columbo says the bird is dead.) and someone simply covered the cage so that no one would have to look at the dead bird.
Suicide by exposure to even large amounts of gas would have been nearly impossible. At the time, the U.S. had long ago converted from carbon monoxide-laden coal gas commonly used decades earlier. Natural gas contains just trace amounts of carbon monoxide, which is unlikely to cause death, barring an explosion.
However, the above is not a goof, as suicide by gas exposure occurs due to the deprivation of oxygen. Any gas that displaces (or sufficiently dilutes the concentration of oxygen can cause asphyxiation.
In the jazz club, there is an acoustic bassist in the band, but an electric bass is heard on the track.
When Alex Benedict sneaks into the garage through the unlocked window to get his car, what appears to be a brick wall shakes, revealing it to be false.
In the beginning of the concert, the shot from camera three is already showing on the "Air" monitor before the TV director says to take camera three. The 'Air" monitor should have had something else on screen (e.g., previous program, a commercial, opening credits to the concert).
The concert's TV director keeps the shot of the trumpet players on the air even after they've stopped playing and have lowered their instruments.
The cameras in front of the orchestra at the concert are not positioned correctly in order to get the two shots of the stringed instrument sections.
Alex Benedict, conducting the orchestra on the TV broadcast with his baton, does not match the music being heard.
Jenifer's hands don't match her piano playing.
When Alex puts his briefcase in his car, there are many cables running along the sidewalk.
When Columbo asks the Maestro's wife what "quasi una fantasia" means, she replies it's Latin for "like a fantasy"; actually, it's Italian. Also, as is proven in later episodes, Columbo is from an Italian family and speaks (and understands) Italian very well.
Alex Benedict is a conductor, yet the grand piano he plays has an obviously stuck white key. This is something no musician would tolerate on any piano, much less his own.
Lt. Columbo states that the maestro's car had been driven while in the repair shop. He comes to this conclusion by stating that the number on the speedometer had changed. The speedometer measures speed, and doesn't record a figure. The odometer does that.
The odometer is part of the speedometer. It's common to make that mistake.
Benedict pronounces Tchaikovsky's name as "chi-KOW-sky" instead of the proper "chi-KOF-sky."
When Alex is lowering the car in the garage, his pristine overcoat is resting on a metal object at his elbow. Being an auto garage, it is likely his coat would picked up some grease spots, thus providing evidence related to him having access to the car during the murder.