Revealing mistake: In the final battle, at one point Sean gets kicked through the boards on some scaffolding, which in turn makes the whole thing fall over dramatically in slow-motion. When Sean flies through the boards that are holding the scaffolding up, however, they way they break and react reveals that they are cheap, light-weight breakaway boards. They break like nothing, don't splinter at all and before the shot cuts, you can even see them wobbling and shaking like they're made of styrophone.
Audio problem: During the final battle, when Sean and Crane start fighting with their arm-blades, listen closely. There's just a few too many "blade clashing" sound effects added in, and it doesn't always perfectly match up to what's on-screen. More were obviously added in to make it seem more dramatic, but it doesn't quite seem "right" if you pay close attention.
Trivia: The first live-action "Guyver" movie had notably tame (often cartoonish) violence and a greater focus on broad comedy in comparison to the darker and gorier Manga and Anime franchise that inspired it, causing some backlash from fans. For the sequel, returning director Steve Wang made an effort to deliver a film tonally closer to the original source materials, and thus added in harsher violence, added significantly more blood to the fight scenes and removed many of the more comedic elements from the first film.
Trivia: Does the main character Shawn seem familiar but you can't place him? That's because he's actually played in this film by famed voice-actor and screenwriter David Hayter. He's notable for many voice-only roles, including playing the main character in the first four "Metal Gear Solid" games, and also worked as a screenwriter on some blockbuster films including the first two "X-Men" movies and the popular "Mummy" spin-off "The Scorpion King."