Strange blank rectangular at the bottom during page scrolling on mobile view

[peppelongo96]

Hi! I think this gif is sufficient to clarify what happens. Look carefully at screen during scrolling... it shows up a small blank rectangular at the bottom. I think is something related to responsive (or not-responsive) background. Have any idea about? For sure, it happens only in the mobile view and it is not related to the background image (i.e. the same using gradient).
Thanks!

[epidrome]

thanks, currently, i cannot reproduce it on safari for iOS and MacOS, it might concern the browser (chrome?), but I agree that the CSS really needs some clean-up #24

just let me know if you find the cause