to be on the wrong track
À mon avis, tes amis font fausse route, petit.
In my opinion, your friends are on the wrong track, kid.
— Paddington 2 (2017)
I was mistaken.
"Une artiste n'a pas à s'expliquer", vous faites fausse route.
“An artist doesn’t have to explain herself”—you’ve got it all wrong.
— La grande bellezza (2013)