When a girl get's stabbed in the belly, position of her clothes shows discontinuity between two continuous shots.
The jeweler speaks of filigree work in conjunction with the scorpion cuff link. Filigree is a delicate tracery of metals, none of which is evident in the object's design.
When a man get's attacked by an ax, assaulter is shown appearing behind him, but he couldn't have been there, as he would be seen. What is more, he is shown running down the stairs after that, so he didn't jump over the railing in the first place, so him appearing directly behind Peter doesn't make any logical sense.
The Killer's face is shown briefly a few times which is obviously not Peter Lynch's (George Hilton), who turns out to be the killer and mastermind behind the Killings.
Lara Floraki's and Sharif's Killer has green eyes (as seen when he cuts open the door to get access to Lara's Apartment). Peter Lynch (George Hilton) who turns out to be the Killer has brown eyes however.
When a girl get's stabbed in the belly, it obviously a fake matter.
Luis Barboo's stunt double's hair is much longer than the military cut flattop he sports.