Pos Y and Height in Rect Transform are replace by "NaN"

Hello,

I'm making a Scroll Rect GUI, all was perfectly working but this morning when I opened Unity, all the PosY in the rect transform was replaced by "NaN", this bug only affect the GameObject in the mask of the scroll rect... And for the Button, in the text the Pos Y AND the Height are replace by "NaN" and I can't change that!

How can I change that? Why this happened? I haven't change anything since yesterday but this happened...

Cordially.

PS: sorry for my bad english