What you were expecting to happen, and what actually happened:
I was doing the class mission event, and i tried to use the bard class to improve all stats of my teams, (third trail) but it seems it doesn’t work properly.
How often does this happen? When did it begin happening?
It happened in class event, in every game started.
Steps to make it happen again
My team are as the attachment and my class is bard with third trail unlocked.