Hi I just made a quick duel against Nyx and his Dragoon Deck, it turns out his second Dragoon used his effect of destroying monsters twice in a row.
I don't know if it's a bug or not, but as I play this card too I tend to know its effects (and by the way it's not the first time I've seen a bug with this card, usually when I cancel my own effect using Dragoon, it doesn't gain 1000 ATK).
Thanks for the help !