Collision box expands when it falls

Hello,

I recently discovered the gravity in UE4, and I am trying to make something very simple.
I have a blueprint actor, when I enter a box collision, it shows up a blueprint widget which says “Press E to take”.
It all works perfectly, but when I decided to add physics to my blueprint actor, I had this strange thing happening :
When my actor is “falling”, the widget pops up “Press E to take”, even if I am NOT in the box collision.

Here is my blueprint : http://puu.sh/pjiqR/abfc93a68f.png
And here is my box : http://puu.sh/pjiTh/f13bc0c3f8.jpg

Another strange thing is that when the blueprint actor stop moving (it has landed), the blueprint widget disappears…

Can someone please help me ? I’m stuck since 3 hours :frowning: