Revealing mistake: At the beginning, when Ivan and the two New York businessmen approach the school, the three are seen through a window from inside the school. If you pay close attention to the reflection of the students in the window, you can see that they are in no way doing anything related to what is being heard inside the school. After the class is dismissed and starts to leave, we see Ivan and the two businessmen begin to enter the school, and if you look in the window, the class is still going hard. (00:03:00)
Factual error: During the karate tournament towards the end of the movie if you'll notice the American flags in the background you'll see that they are displayed improperly. Whether flags are being displayed horizontally or vertically, the stars should always be on the left side of the flag.
Continuity mistake: In the tournament at the end of the movie, when Dean and Ivan meet in the center of the ring before the match, we can see that Ivan's stance has his back to our view. However, when the shot sweeps over the crowd and judges, and then back to Dean and Ivan, we can see that Ivan is now facing us.
Continuity mistake: in the scene where Jason does his own training by kicking and dodging the moving sandbags hanging down, he finishes by kicking each bag individually. Look closely - one of the bags is only being held together by a thread, so when Jason kicks it, the bag splits open quite easly. (01:06:45)
Continuity mistake: In the scene where Bruce Lee is teaching Jason how to kick while his other foot is being held in a noose, Jason is wearing a grey jumper and black pants, however a shot is shown of Jason tightening the noose around his ankle while wearing a yellow tank top and a wrist band. Cut back to Jason and Bruce talking and not only is Jason wearing his grey top again but the noose has somehow managed to loosen itself. (01:04:35)
Continuity mistake: This mistake is in the scene where Jason finally manages to kick the sandbag with his foot in the noose. Before Jason performs the kick, there is a clear knot in the rope, however, in the slow motion shot, the rope is not knotted. Afterwards, the knot is back. (01:04:35)
Continuity mistake: Van Damme rips his shirt off and drops the gloves. Starts circling his young opponent. You can see the items he drops but a couple of shots later they are in the corner in different position, which will change again when he brutalizes the opponent against the ropes. (01:34:00)