Layer not render properly. Why?

Hi,

I have an issu and i don’t know why. When i move, my background layer are not rendering properly. Do you know why?

What i see is that

if a move a little bit you can see that the rocks come in front.

I don’t understand why because the first element is on -6000 for the distance and the second one is -7000.
At the start it’s ok, but if i move a little bit, it’s not ok, and i have that issue on all my layers…

Please Help.