foliage issue

Hi everyone !

I have a little issue with my grass foliage, when I am in the editor with my lighing calculated it works fine but when I play or cook my grass looks bright and seems to have no shadow. Is someone have the same issue than I ?"]

If it can help I have this problem only on my persistant level, I have a level streaming with other map in it and this grass problem appears only in my persistant level with all my maps in it. when I open my level with that map only it work fine :confused: