The hitboxes that are drawn in debug mode aren't drawn accurately when doing attacks on sloped surfaces. For attacks that angle with the ground the character is standing on, the hitboxes that are drawn for them get less accurate as the ground's slope approaches vertical. It just seems to be the hitboxes that aren't drawn correctly though; the 'actual' hitboxes are in the right spot.
Moves like Ganon's down taunt and Roy's down tilt and side smash show this glitch very well:
The drawn hitboxes don't follow the actual hitboxes of Roy's sword, which in this picture is going through the ship. The hitboxes being drawn clearly hit Ivysaur, but he's not getting hit:
Moves like Ganon's down taunt and Roy's down tilt and side smash show this glitch very well:
The drawn hitboxes don't follow the actual hitboxes of Roy's sword, which in this picture is going through the ship. The hitboxes being drawn clearly hit Ivysaur, but he's not getting hit: