[Theme: Zerif Pro] "Jumping" menu after centering logo

Hi!

I′m using the following code to center the logo above the menu, center the menu and leftalign the text in the submenus in the theme Zerif Pro.

/* Place logo in center above the menu and center the menu */
.navbar-header.responsive-logo {
text-align: center;
width: 100%;
}

a.navbar-brand {
margin: auto;
float: none;
}
.navbar-brand > img {
max-height: 100%;
}

/* Leftalign submenus */
.navbar-inverse .navbar-nav ul.sub-menu {
text-align: left;
}

However, this makes the menu “jump” down one row and a little bit to the right when pressing any link in the menu, and then return to the center again. You can try it out at https://www.skult.se.

I also tried the following code, but the exact same thing happened, and also the menubutton stopped working in mobile view.

/* Place logo in center above the menu and center the menu */
.navbar-header {
width: 100% !important;
text-align: center !important;
}

.navbar-header a {
display: block !important;
float: none !important;
}

Any ideas? I can′t figure out when it stopped working, I didn′t notice until yesterday…
I killed all the plugins except Simple Custom CSS, and removed all custom CSS except the above with the same result.
Could it be with the latest theme update? Latest WordPress update? I really don′t know/remember, but I′m pretty sure it worked before as I haven′t noticed it until yesterday…