After reaching a position where you have a chance to destroy Onimaru’s bots, it’s very easy to slightly misspace or mistime your attack and end up knocked down, losing that advantage, taking damage, and receiving Onimaru oki.
As far as I can tell, if the bot’s hitbox were further back right at the base, it’d be easier to time low strikes to beat it. If the hurtbox were extended further forwards it’d make timing more lenient in general with minimal impact on the bot’s strength otherwise. Such a hurtbox extension would need to be projectile invulnerable to retain current projectile trade behaviour, I think?
(From a discussion in the #fantasy-strike channel of the Discord server a few minutes before this post)