Windmill + Acetone + Celluloid + Firing Pin - S4-E4
Factual error: While the collapsed building is described by Matty to be located in Karlsruhe, it's actually in Heidelberg (as seen by the famous castle on the left and the river Neckar with its bridges). (00:05:15)
Rails + Pitons + Pulley + Pipe + Salt - S5-E9
Factual error: Mac's "cutting torch" was supposed to weaken the lock, and the pressure difference would do the rest, since there was "no air in the room." However, the door swings outward. If there is no air in the room, the higher pressure outside the room would keep the door closed, working against him, rather than for him. Besides this, the arc from a 12v car battery is unlikely to considerably weaken a steel lock. (00:01:15)
Barn Find + Engine Oil + La Punzonatura + Lab Rats + Tachometer - S5-E13
Factual error: MacGyver is wearing what is supposed to be a US Navy uniform. But he has the shoulder epaulets of a Lieutenant Commander, and is wearing a Chief Petty Officer service cap. (00:00:30)
Diamond + Quake + Carbon + Comms + Tower - S5-E10
Continuity mistake: MacGyver is running in Mexico City and runs into a car with driver coming down the road. When he gets up, the car is parked and no-one is inside. It is the same car with the same license plate. (00:10:10)
Rails + Pitons + Pulley + Pipe + Salt - S5-E9
Factual error: MacGyver is using an improvised cutting torch to weaken a lock on a door. When he thinks he has cut enough he drops the torch and immediately holds on to the lock to open it. If It has been subject to a cutting torch long enough to weaken it, he would not be able to grasp the lock with his bare hands without seriously burning them. (00:15:00)
Diamond + Quake + Carbon + Comms + Tower - S5-E10
Other mistake: MacGyver makes a diamond in his kitchen to mount on a ring to propose to Desi. He shows it to Bozer, and - miracle of miracles - it is already faceted. (00:01:30)
Rails + Pitons + Pulley + Pipe + Salt - S5-E9
Factual error: Every time the Phoenix Foundation airplane is shown, it has absolutely no markings. Every aircraft has to be registered somewhere and display its registration prominently, and no aircraft can fly in a country's airspace without a registration number at the very least. (00:01:55)