Dynamic object all switch to left when flexible layout

I have a problem were my dynamic object that is place on the top of the page would not fall down equally in the width of the page.

I place 3 square side by side, one on the left side one in the middle and one on the right side.

with these parameter

width scale activate 100%
each square have metric: pin left, top, right
all dynamic

they should fall down one on the left one on the right and one in the middle, but they all fall stack on the left side of the page

I dont get it, it was working before, i tried on two computer and if does the same strange thing…