Plot hole: The whole problem with the teleporter occurs when fly DNA is mixed in with Seth Brundle's DNA, starting his transformation into the Brundlefly. Brundle is on a hiding to nothing from the word go, and the fly is irrelevant. Humans are a walking talking mass of foreign DNA - we are host to one trillion bacteria all of which has a complete complement of DNA, as do various tiny mites that live in our hair follicles and all sorts of single cell organisms in our gut. If the transporter serves to mix the DNA of all living creatures which are in the transporter pod at the time Brundle would turn into a half-man, half-bacteria. Incidentally, DNA from a bacteria, an amoeba or a hair follicle mite would be just as 'compatible' with human DNA as that from an insect. It's quite a simple chemical, really.
Continuity mistake: When Terri is at the party, her blonde wig changes shape and size many times.
Revealing mistake: When Ripley first burns the egg plants inside the nest, the Queen screams and moves her head. The steel rod used to hold the Queen's head to the rest of her body is easily visible.
Continuity mistake: When William Petersen is talking to his kid in the supermarket, the cereal boxes behind him on the shelves change between two shots. The items behind Kevin also change during the scene. (01:09:05 - 01:10:20)
Visible crew/equipment: When Alan is struggling with Barbara on the drawbridge, the shadow of a camera/operator is on Alan's back as they get near the car. (01:30:30)
Audio problem: A soda can that is supposed to be full hits the man. When the can hits the ground you can hear that it's empty.
Other mistake: In the final scene of the movie, Megan starts a boat motor and uses the propeller to hit Jason in the face, who has been chained down underwater. But if Jason can only barely reach her foot from underwater, there's no way the boat propeller is underwater far enough to reach his face. (01:17:50)
Suggested correction: The boat was driven a good ways, it's not like they were shallow and then all of a sudden deep. They were deep for a little bit. I mean not so deep like the ocean, but it was a good enough ways for someone to drown. Megan is tall for a girl and Jason is a big guy and the propeller is right at his head/neck.
You are very much mistaken. The boat propeller is too high to reach Jason's face.
Factual error: When the Delta Force lands on a beach, prior to their assault, their landing craft is lit up like a christmas tree. The commandos wear dark uniforms and have blackened their faces, but they also carry bright white ropes around their chests. Some of them are scuba-divers, wearing yellow oxygen-tanks. In short, in the real world they would have been spotted within minutes.
Continuity mistake: In the sedan/pickup chase, both of Cobra's headlights are shot out at the start with pinpoint accuracy. A minute later as the cars race down the freeway, the holes where Cobra's headlights used to be are filled with black plastic discs.
Factual error: Right before Frank humiliates Dorothy for the first time, he blows out one of the gaslights in her apartment. That is never done in real life, for the same reason you would not blow out the pilot in your stove.
Continuity mistake: Rolland Tyler (the set-up special effects guru) and his F/X assistant Andy have one of the "dirty" cops in the truck of an old car. To get a confession out of him, they take him to a secluded place under a highway overpass and continue to ram the car, trunk first, into the overpass pillars with the cop still in the truck. The man buckles, but not before about six rear-end hits. Yet, there is very little dents or damage to the back of the car throughout the ordeal.
Revealing mistake: The "blower" on the yellow Firebird never runs. NO wonder he couldn't beat the Wraith. (00:44:10)
Continuity mistake: During Kevin Bacon's race with fellow messenger, the scenes shift back and forth from New York to San Francisco. In one city, he's on a fixed gear (no freewheel on back wheel) and when the race is taking place in the other city, he's riding a single-speed. Basically, the cityscape and bicycles switch from scene to scene.
Continuity mistake: During the very last scene with all of the Freelings, Taylor and Tangina, right after Taylor leaves alone in the Freelings' car and the Freelings start walking down the street, the camera pans back so you can see the whole neighborhood including where they were just standing. Where did Tangina go?
Continuity mistake: When Jim pushes John out the car, in the shot where John is lying on the road, his head is on the road's white stripe, yet when it cuts to a closer view, his chest is on the white line, not his head. (00:12:30)
Continuity mistake: When Eddie and Michel are in the police station and Losado comes to pick up Michel, her hair clip is on the left side of her hair. After Losado and Michel get into the car, her hair clip moves to the right side.
Continuity mistake: When Jim and Brandon are knocked into the water, Brandon dies, but somehow manages to grab hold of Jim and pull himself up.
Factual error: In an early scene, the high school science teacher produces a schematic diagram of the two nuclear bomb designs created by the Manhattan Project. He says, "Here are two designs based on plutonium." Actually, only the Fat Man bomb uses plutonium. The other, the Little Boy design, uses uranium.
Continuity mistake: Harrison Ford and his character's family are all huddled on a beach being pummeled by the wind of a powerful hurricane, but visible in the background are a couple of palm trees standing perfectly still.
Revealing mistake: When Sean Connery and the others are examining the corpse found in the water, the dead body's eyes blink. (01:01:05)
Suggested correction: Being as how the bacteria and mites and such were IN or ON Seth, the machine was able to organize those symbiotic relationships accordingly as teleporting one would teleport all. The fly was separate, not touching. The machine was not programmed to anticipate two separated entities and so combined them into one on the other side.
Phixius ★
We leave behind a vapour trail of bacteria and viruses (among other things) as we walk, in our breath and emanations from pores in our skin, and Brundle isn't trapping any in his clothes as he isn't wearing any. Brundle has an invisible cloud of DNA floating around him in that teleportation chamber and as far as the machine is concerned their DNA has exactly the same status as that of the fly.