the ui elements are anchored to stretch to all sides of the screen in UI canvas. However, when building, the ui elements appear to be moved half a screen to the right and half a screen to the left. It's as if the entire object is reanchored bottom left and then the position is reset to 0.
I can fix the problem by adding a set rect transform action to the starting state of each of these ui elements with the value x and y = 0. So I managed to hack a fix together but I don't think it's supposed to behave this way.