Continuity mistake: While running on the mountain, the stunt double is wearing a white shirt while MacGyver is wearing a blue shirt.
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)
Continuity mistake: MacGyver appears to be a novice at mountain climbing, but in the very first episode he mountain climbed like a professional.
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.
Other mistake: Spencer somehow manages to get shot even though the bad guy never points his gun at her.
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)
Continuity mistake: The episode begins with MacGyver's Jeep having a blowout and going off the road, however, when we see the overturned Jeep, all 4 tires are inflated. (00:01:45 - 00:02:15)
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.
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.