Problem with child theme

Hi.
I have a curious problem.
I’m using Undiscovered theme and I’m very glad.
I’m using child theme with the instructions of WordPress codex page (even in another site with another theme and is ok).
When I use Google Chrome and I go on the page of my web site the first 15 second (about) I see big size chars.
And then return to the default size.
I tried to return to the parent theme and it works well.

I tried too to leave just the first instructions in style.css of Undiscovered child theme without change anything:

/*
 Theme Name:   Twenty Fourteen Child
 Theme URI:    https://example.com/twenty-fourteen-child/
 Description:  Twenty Fourteen Child Theme
 Author:       John Doe
 Author URI:   https://example.com
 Template:     twentyfourteen
 Version:      1.0.0
 Tags:         light, dark, two-columns, right-sidebar, responsive-layout, accessibility-ready
 Text Domain:  twenty-fourteen-child
*/

@import url("../twentyfourteen/style.css");

/* =Theme customization starts here
-------------------------------------------------------------- */

Where obviously in url I have:

@import url("../undiscovered/style.css");

and the other informations are for undiscovered theme, but it works well just with (default) parent theme.
I wonder why.

I like a lot this theme, you (themeshaker) made a good work.