Expanding menu leaves white lines below screen

depending on the device i use..if i expand the menu that goes beyond whatever screen size, white lines appear on the bottom and i need to re-collapse and re-expand to see the rest

is this fixable with css?

you can see it on onestop.drzvrs.com

am able to replicate this on both the desktop and mobile devices

thanks

phil

https://www.ads-software.com/plugins/responsive-menu/