Finally i found a solution. So i want to thank myself
It was easy.
All my animation was gathered inside a group. That moving group had the flexible/responsive settings. I though that i could remove those responsive settings and try to put that group in another group and set the responsive options for that last group.
And now i'm happy.
If you're curious here is the example
test-scroll 2.zip (431.1 KB)
And please, forgive my scrummy crummy english !