Other mistake: In the scene when the helicopters arrive over the research center, look at the heli in the bottom right - it just fades out, while one on the left materialises, and the one in the middle changes position. Notice that after all the helicopters have changed place, you can see the helicopter that faded out appear on the helipad. (02:25:25)
Continuity mistake: When Helen is trying to stop Hercules from beating her friend, her hair runs down along her back. A shot later, it's over her left shoulder.