I found animation error in Bakugan Gundalian invaders episode 21,in this episode at the beggining Drago is Pyrus Helix Dragonoid,and not Pyrus Lumino Dragonoid that is the drago he was in previous
List of Bakugan Battle Brawlers Gundalian Invaders DVDs - The Bakugan Wiki
The Gundalian Invaders Japan though... (Subtitles by me) : r/Bakugan