Foliage shadow is not moving ?

Hello,

I don’t understand why the shadows are not moving with the wind effect of the foliage. I would like them to softly move to create a nice effect but they are totally static. I am usiing pathtracing for better render.
Maybe someone here could help me ?

I am using the new megascan tree pack.

Here is a video showing my issue.

Thank you in advance and sorry for my english.Shadow issue example