Thank you for trying, I just got an e-mail from Panic (Coda 2) telling me how to fix te problem and it helped me a bit.
In my preferred languages French is the first and Japanese was second after my update to Yosemite.
So i took the english and replaced it with the japanese. And it works !
My Coda 2 is now in english witch not a problem for me, but there is always this bug who somehow takes the second preferred language.
(Sorry for my terrible english guys)