The Most Dangerous Match - S2-E7
Other mistake: The police photographer takes a picture of the garbage grinder. His camera has a flash, and the photo is indoors, but the flash does not fire.
Character mistake: In the grocery store scene Robert Culp sits on a display of pumpkins but there are 2 signs that say watermelons.
Suggested correction: As a retail worker of 18 years, I know that POS (signage) mistakes happen in supermarkets, for example a product is moved and the correct POS is not replaced. This scene seems to be filmed in a real supermarket meaning this is not a mistake made by the show's producers, however if this was filmed in a studio, "Character Mistake" would be the wrong category as the mistake would have been made by the set designers.
While I've never seen mislabeled items I know mistakes can happen. But since the characters aren't real, every mistake they make is the fault of someone on the crew, whether it's the actor, writer, or set designer. For example, misspellings are considered character mistakes (unless intentional), even though it would have been made by the person who created it.
Continuity mistake: There are several views of Uncle Jarvis in his (beautiful) Bentley S2 Continental from the front. We see the inside rear-view mirror, and it is correct. When we see him spot the police behind him through the mirror, it is a different mirror and not the correct one for that car.
Character mistake: After Columbo disturbs Dr. Kepple and his ball goes in the rough, Kepple says they are playing for rather high stakes. He picks up his ball, looks at it, and places it back on the ground. In a high stakes game, that would be cheating, and the other players would not have tolerated it.
Factual error: Several times, the revolver used to murder the singer is referred to as a "Weatherby" or "British Weatherby." Weatherby is an American manufacturer of rifles and shotguns; they do not make handguns. The revolver used is a Webley, which is of British manufacture.
Continuity mistake: At the cafe when Columbo talks with the police officer his cigar is in his hand in the back shots but disappears in the front shots.
Character mistake: Kingsley carries a briefcase in to the attorney's office, but leaves without it.
Caution: Murder Can Be Hazardous to Your Health - S10-E2
Continuity mistake: When Sheba the dog scratches Anders' car her claws are on the glass and the top of the metal part of the door, above the character line. In the photo that Columbo shows, the scratches go much further down the door.
Character mistake: Columbo took the Beretta off the gun display by inserting a pencil into the barrel of the gun. In a previous episode, he said to NEVER insert a pencil there because it will ruin the groove of the barrel, making it impossible for ballistics to get a match on the bulletin. When using a pencil, Columbo picks up a gun up near the trigger.
Character mistake: When Columbo is in Mr Benedict's house with Mr Benedict, he calculates the cost of Mr Benedict's house at $720,000. A moment later Mr Benedict asks Columbo; "How did you arrive with that figure, $750,000?" (00:43:20)
Continuity mistake: Just before Viveca murders Martin Sheen, she scribbles an amount on magazine-her nailpolish is red. Seconds later after the murder with the microscope, Vera's nailpolish is a completely different color, mauve.
Character mistake: Twice, Brenner refers to the T-33 aircraft as the Silver Star. The name of the T-33 was the Shooting Star.
Factual error: Santini murders Jerome using a revolver with a silencer. Although this is one of the oldest Hollywood tropes, a silencer (properly called a suppressor) does not reduce a gunshot to a whisper; it only cuts the noise to about 110 dB, which is still very loud. In addition, suppressors do not work at all on revolvers, because most of the noise is generated in the gap between the cylinder and the barrel.
Factual error: All LAPD officers must re-qualify with their weapons multiple times a year. If indeed Columbo could not "hit the target," as he says to another detective, he would never have made it through the police academy, much less have become a detective and have been promoted to sergeant and eventually to lieutenant.
Factual error: Columbo gives another detective $5 to go to the gun range for him. Technically, that is a bribe and it would cost both Columbo and the other detective their badges.
Other mistake: When Columbo is examining the crashed Jaguar, we see silvery tape around the opening where the smashed headlight had been. The tape shouldn't be there.
Short Fuse - S1-E7
Plot hole: We are told several times that the road to the mountain house is very narrow and difficult to negotiate. How did the very large crane get there so quickly to lift the bodies after the crash?
Undercover - S12-E3
Continuity mistake: When Krutch speaks to Columbo on the phone about 40 minutes into the show, his voice sounds like he has a cold. Earlier and later in the show, his voice doesn't sound like that.
Character mistake: Columbo talks to the cardiologist. The doctor gives him information about his patient, Mr. Williamson. Columbo has no warrant, so the doctor is violating privilege. He wouldn't give that information to Columbo.
Dead Weight - S1-E4
Other mistake: Columbo goes into a diner and has a bowl of chili. The cook asks if he wants his coffee black. Later he asks if he wants cream and sugar in his coffee.