Continuity mistake: When the Villains send their cronies (for example, Putties, Tengu Warriors, Cogs, Piranhatrons, etc.), their numbers constantly change from when they arrive, to when they leave. This is due to the use of Japanese footage used from Kyoryu Sentai Zyuranger.
Other mistake: Episode 13-12: "Shadow (2)." When Cruger is challenged to defeat 100 robots, a red countdown meter appears on the screen, ticking down each time Cruger dispatches an opponent. When the counter is at 21, Cruger slices his sword at a robot, which then goes down. But the counter stays at 21 and only goes to 22 when he slices at the next robot. Every robot in the sequence goes down after a single hit from Cruger's sword.
Plot hole: Quite often the Rangers were contacted at school and would teleport to the command center, danger zone, etc. It is safe to say that the faculty would notice star pupils missing classes so often, yet it was never questioned or addressed.