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.
Plot hole: When Terry gets back to her computer, after escaping from the spies and cops, the time is after 3pm New York time. If Jack actually is in Russia or Eastern Europe, wouldn't he have already gone to, and been killed at, that 5pm meeting?
Plot hole: After Leo and the clerk finish looking up the fingerprints on the computer, the other cop says that the dead girl was dating Roland. When asked about Roland's address, the other cop says that he can probably find it somewhere and leaves the room. Leo is sitting directly in front of the computer that just gave them someone else's address. (00:47:10)
Plot hole: How did Tommy get Jason's mask? I don't think the police would let him keep it as a souvenir.
Suggested correction: This is not the same mask from the previous movie.
Yes, it is. It even has the ax mark from the end of the third movie.
It is a very different mask. The only things that match are the shape and the axe wound. The color changed from yellow to almond. The straps changed and snap on buttons that attached the straps were replaced with rivets. The half missing large red chevron has been replaced with a red triangle. The two smaller triangles under the eyes are gone. All the damage and chipped paint from part 4 is missing. This mask has more in common with the mask in Tommy's dream in part 5. My opinion - Tommy made it.
Plot hole: Throughout the film, Mitchell's main reason for not contacting police is that his affair and his mistress' murder would become public, derailing his wife's election and thus destroying "the one thing she built for herself". Seems odd that part of his plan is to rig his own car with explosives (from his own company), give it to the lead bad guy, then blow him and the car up on a public bridge. Certainly not a 'character mistake' as the tone of the film's ending is that, somehow, he has won, when he's failed in spectacular fashion to keep it all quiet- and his wife's been drugged, beaten, raped, and her career is over, while he's going to jail for murder.
Plot hole: Near the end of the movie, when Packard is about to race the Turbo, he puts on a helmet. Where exactly did he keep this helmet? The '77 Corvette is a two-seater with very little storage space for the passengers. Oggie and Minty's helmets could have been in the back seats of their cars.
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.