Bug in Bakery Demo UI with Chrome and small Displays (width <=600 px)

We’re using v.8.1.4 and did build an application with a similar navigation mechanism of the Bakery Demo.
Please start the Bakery Demo (https://bakery.demo.vaadin.com/#!storefront) in Chrome an shrink the width <= 600 px so that the left sidebar will disapear.
Call the “Storefront” view an try to click the green “New” Button or try to focus the search field. It only works when clicking in the lower area of these components. This is a really problem when using our App with mobile devices.
It seems, that invisible parts of the navigation bar (z-index: 10.000) covers these components.

Firefox, IE and Safari works fine. Is this a Bug in Chrome Browser or in Chrome adaption of the Vaadin Framework components?
Does anyone have any idea how to circumvent this problem?