Deliberate mistake: Many of the Rangers in the Legendary Battle could not be there since they were portrayed by the same person. All 3 Rockys, all 3 Adams, and both Jasons and Kimberlys were all present.
Other mistake: Tommy appears as the Green Ranger; this is not possible since his Green powers were lost forever in MMPR season 2 which led him to becoming the White Ranger.
Continuity mistake: When they are showing every past Ranger rescuing someone. In the part with the rocking car, Tommy comes down on the car, he reaches for the boy with his left hand. Show above view, he's holding his right hand. Switches to the front view, left hand again.
Visible crew/equipment: When the Rangers are talking to Tommy and the other Rangers, the pink ranger helmet is reflecting the mic above.
Continuity mistake: Troy's morpher was destroyed yet when he is being held for ransom, he is in his ranger costume.
Other mistake: The legend rangers have cameos where their Ranger helmets reveal which team they fought with. Tommy has the White Ranger helmet appear and even uses Saba (his White Ranger weapon) to rescue a child from a car but he actually fights as the Green ranger in the war.
Visible crew/equipment: You can see cameras, crew and what appears to be a bonfire reflected in Emma's visor when she is dressed as the White Wild Force ranger. (00:15:00)