black line 3/4 of the way down page- mobile only

Hi!

I am having trouble eliminating a very thin black line that appears on the mobile version of the site towards the bottom of the screen. It only appears on scroll and gradually disappears when you stop scrolling.

I’m not sure what CSS to add to remove this.

I’m using the theme “blogfeedly”

thank you!

The page I need help with: [log in to see the link]