There is an error in the page

[manuel (Manuel Kostka)]

Looks like a bug to me as well:

It’s caused by this declaration in /app/assets/stylesheets/common/select-kit/category-drop.scss:

What you could do as a temporary fix @tachibanalolo is either over-ride that rule using the default padding:

.select-kit.combo-box.category-drop {
  &.bar.has-selection .category-drop-header {
    padding: .5em .65em;
  }
}

Or choose a different category style (other than bar) as the rule only applies to that style.