Problem with ground

Hi all…
Why, only in this level, i have a problem with the platform and the ground? When i jump on it, if i m moving, i slip on it…
As this: https://postimg.org/image/euz00t67f/
My character goes in the Jump animation and stay still until he stop to slip… Why?
I m having strange trouble from a while. In another my background(that was in -100(the green variable) and my platoform was in 0 as position was under my background…
Why?