Why viewport resize at start?

Hi, when I start the game, all elements have a weird render like there’s a size or resolution problem. After some time everything resize well.
Editor: Need less than a second.
On iOS: I need to move the device, put it on a flat surface to force the resolution.

I don’t know if it’s related, but when I open a widget, the text take all the width space during some milliseconds before correctly resizing (not only the text but other elements changes).
It happens on all widget.

thanks