Other mistake: Spencer somehow manages to get shot even though the bad guy never points his gun at her.
Continuity mistake: When MacGyver drives the forklift into the car one of the forks goes through the windshield. When the shot changes it is now out of the window. You can see the broken windshield where it had gone through.
Visible crew/equipment: When the pursuing police car exits the sewer, two mannequins can be seen in the driver and passenger seats. (00:42:35)
The Gauntlet - S1-E4
Visible crew/equipment: While Macgyver is running into the desert, a camera is visible in the far right of the screen. (00:05:07)
Visible crew/equipment: As they drive the car out of the plane with a parachute you can also see someone else (another camera man probably) jump out right behind the car in the same shot. (00:45:30 - 00:46:05)
Factual error: Some factual errors regarding Basques: 1) Basques have not been fighting for ages against France and Spain, and they do not kidnap US citizens. 2) Basques do not look, in any way, like South Americans. 3) Violent Basques are not guys "up on a mountain" with old rifles, but terrorists with modern weapons.
The Prodigal - S1-E9
Continuity mistake: When the car breaks down and MacGyver backs up the tow truck he hits the Fed's car, but in the next scene after he gets out of the truck it is feet away, he never moved the truck.
Flame's End - S1-E13
Visible crew/equipment: As Amy and MacGyver are chased around a nuclear reactor just before the bad guy gets nuclear steam on him, you can see a pair of legs in a top row window around where they are walking. Remember the nuclear reactor was hot with radiation so no-one would be wandering around.
Flame's End - S1-E13
Other mistake: MacGyver and Amy get locked up in the nuclear disposal chamber with the sludge coming for them. Amy says "before it reaches this room it will get too hot for us to breathe", but just as MacGyver closes the door after managing to get it open, the sludge pours in. At this point they're breathing just fine and not sweating at all.
Character mistake: At the border crossing during the car chase there is a mistyped sign below the window reading "Bunesrepublik Deutschland". it should be "Bundesrepublik Deutschland" (00:07:45)
Factual error: MacGyver and Victoria go back to the location of the science event to think about the incident. MacGyver's friend, Bannister, suffers from a heart attack. MacGyver cuts a microphone cable and binds the cords to a metallic candlestick. MacGyver uses his creation as a some sort of defibrillator. Of course it works and MacGyver saves his friend. The maximum power in the wire is 11-48v DC with the maximum current of 10MA - not enough for giving huge electric shocks.
A Prisoner of Conscience - S1-E21
Continuity mistake: When Pete steals the drugs, he puts them in his pocket and drops a bag right near the door, but when the doctor comes in and finds it it's much farther away from the door than where he dropped it.
Continuity mistake: When Tommy is escaping into the mountains to try and help, a small bit of his jacket tears off onto a tree branch. MacGyver later sees it, but the branch that the torn piece is on looks entirely different. (00:21:10 - 00:22:10)
Jack of Lies - S2-E6
Audio problem: At night when MacGyver and Jack are sneaking past the guards behind a mule, we see about 8 to 10 light bulbs hanging overhead. MacGyver later pulls the cord down and all the lights begin to pop. There are about 16 pops, many more than there were bulbs on the cord. (00:24:50)
Jack of Lies - S2-E6
Continuity mistake: When MacGyver et al. spot the car they will use to escape, the headlights are clean and white. After the commercial break, they are much dirtier and the dirt is only on certain precise spots on the headlights. (00:33:15 - 00:35:25)
Continuity mistake: When the Golden Eagle is shot with the crossbow by the man, It goes through it's wing. Later when MacGyver comes to try and take it out, it is in a different position on the bird. It is not through the wing anymore. (00:07:25 - 00:09:15)
Continuity mistake: While running on the mountain, the stunt double is wearing a white shirt while MacGyver is wearing a blue shirt.
Continuity mistake: During the car chase through the desert, the rear view mirrors on both cars disappear and reappear repeatedly.
Continuity mistake: The bullet hole fired into the red Cadillac by the bad guy later disappears.
Continuity mistake: In the opening scene, the hitmen's car loses a hubcap as it chases mobster Tony. In the following shots, however, all four of the car's hubcaps are back in place.
Answer: Late one night, Geoffrey used a covert listening device to overhear David explaining his barricade device to Janet which is how he figured it out.
How do we know Geoffrey really did use a covert listening device? They didn't mention him using one.
There was a scene of him using it when David told Janet about his barricade.