Minairuka doesn't do either of it's two effects - it doesn't have the option to special summon itself when a WATER monster's effect is activated, nor can it banish a monster to negate a card on the field.]
Bug reproduction steps
[`Have Minairuka in hand. Activate any water monster’s effect (like Ghoti) and Minauruka will never get a prompt to special summon itself from the hand.
Or have Minauruka on the field, and it will never have a prompt to banish a monster on the field. It just sits there.]
Screenshot OR error code
[`1. If a WATER monster’s effect activates, Minairuka should receive a prompt to special summon itself from hand.
While Minairuka is on the field, it needs to be able to banish a WATER monster to negate smoething. .`]
What OS are you using