The victim's eyes are peacefully closed as he lies on the rooftop, thoroughly drugged, until he is shoved off the building. When Gabe's body hits the pavement, his eyes are wide open. Writer Jeff Cava admits that everyone failed to spot this goof in multiple screenings during production.
At the end, when Columbo shows Crawford the "love note" written by Gabriel, it is written in a different, round, curly script than the original, which had a more angular script.
The computer printer that prints the music score is accompanied by the sound of a dot matrix printer, when the printer is clearly an HP 4MP Laser printer.
When Columbo goes into Findlay Crawford's dressing room/bungalow, the light switch near the door has both switches flipped in the "up" position. When Columbo and Crawford leave the room, the switches are in the "down" position, and when Crawford flips them "up", the lights go out.
The size and placement of the broken champagne glass pieces change from when it first falls on the floor and breaks to when Gabriel collapses next to them.
In the mortuary, the murder victim has no post-mortem Y-incision when Columbo looks at body, yet the autopsy report has been completed.
During the opening credits, the portable stereo that reproduces the live music from the recording studio is seen. As the camera pulls back, the stereo set's VU (Volume Unit) meters come into view; the meters' needles are not moving as they should be when the music is playing.
There is no way Columbo would have been allowed inside the studio during a recording session.
While listening to the concert recording, Columbo calls out to the studio engineer Nathaniel to "bring down" the music so as to isolate the creaking elevator sound. Nathaniel would not be able to do this in a regular recording studio; the only place that would have the equipment to do so would be a police forensics lab.
"This Old Man" is the song often whistled or sung (in part) by Columbo throughout the show. At the end, Columbo asks Rebecca to teach him how to play "This Old Man" on the piano. However, in Try and Catch Me (1977), which aired decades earlier, Columbo plays the first couple bars of "This Old Man" on his own. However, this should not be considered a goof for a couple reasons. Columbo may have been trying to get Rebecca's mind off her lover's murder, plus it is unrealistic to expect continuity of minute details in an episodic series that aired over a period of decades.
When Columbo is on the roof after the body falls, his hair is blowing in the wind and the Sergeant's tie is waving about, but the sheet music remains where it fell.
Not surprisingly, non-conductor Billy Connolly's attempts to appear like a conductor are tenuous at best. He shows none of the accepted beat patterns a real conductor would use when conducting music.
One minute and 58 seconds is an unrealistic time for an elevator to reach the roof of a 4 story building. Assuming 6 floors from the basement to the roof, it would take 20 seconds to reach each floor. Combined with the flashes inside the elevator demonstrating how fast the elevator actually moved, it proves the time frame set was more convenient for story line.
The crumpled brown bag Columbo carries around in the earlier scenes suddenly becomes like new when he brings it into the music studio. Later in the show it's crumpled, and in the very last scene, it's new once again.
The victim would have been quite sunburned after having been on the roof for several hours prior to being dumped off of the building by the lift doors.
Near the end, there is an overhead shot of the roof with Columbo and the murderer coming up the elevator. The shadow of the camera and crane is visible in the lower left corner.
A camera shadow can be seen on the locksmith's van at the apartment of the murder victim.
(at around 21 mins) While on the roof, when Crawford is about to put Gabe's body on top of the elevator doors, a yellow metal tape measure comes into frame on the left side.
In the opening, Crawford's conducting does not match the tempo of the music being played.
Columbo asks Rebecca to show him the simple notes to This Old Man on the piano because it's the song his wife hums while cleaning the house. He previously played simple notes of it in Try and Catch Me (1977).
When Crawford times how long the elevator takes to reach the roof, when it pushes up the roof doors, it knocks over a music stand that McEnery had put over one of the doors. When Crawford takes McEnery's body up, the same music stand is knocked over again, yet there is no reason why Crawford would have placed it back over the roof door.