Menu disappears on first request behind slider

Hi there,

the Menu disappears at the first request of the site www.dts-print.de . This is only with firefox quantum 59.0.3 (latest version, no updates available). The Menu is available after the first scroll-action. After this, the menu is still available.
Maybe you could help?

First request:

Kind Regards, Anton

Here is the menu, available after a horizontal movement:

Kind Regards,

Anton

Hello Anton,

Please try to temporarily deactivate all your plugins except aThemes Toolbox and Page Builder by SiteOrigin, activate parent theme, and see if it helps.

Kind Regards, Roman.