i get often your same issue.

in my specific case happens because i run this lineup:

x kisame samehada x

x x x

WM hokage minato AGK

with sand dust.

I use sand dust in round 1 with the consequence that koh + high combo mystery let me steal chakra from the enemy.

if i'm on auto as soon as i steal the chakra kisame uses his mystery too.

if i'm not on auto at the moment the *on of kisame mystery enlightens, letting me click the keyboard *on to cast it, it's just too late and i can't avoid that the enemy move 1 standard attack resolves (kisame uses his mystery after the whole animation of the enemy move 1 standard attack).

This is the issue that people call 'mystery delay issue'.

It's linked to the fact the UI doesn't let you click on the mystery when is available but only when the whole animation that unlocks it resolves and most of the times this animation is not on synchro with the enemy standard attacks turns.