Animations / Sticky Position only working in reverse

Hi, I’m having a weird problem. My site works as intended for everything in preview mode, and for desktop when published, but not for mobile only when published. On the second page the sticky position doesn’t seem to work ONLY when scrolling down…yet when I scroll back up it works just fine in reverse. I tried to look into overflow settings since I saw that that was a common issue with sticky position, but I can’t find anything where overflow is set to anything but visible.

The published page is here: ch02

Not sure where to even begin looking for the problem at this point. I am (obviously) quite new at this and have basically learned just what I needed to achieve the effect I was looking for (I’m making a scrolly story webcomic). Any advice would be very much appreciated. Thanks.

Here is my site Read-Only: LINK
(how to share your site Read-Only link)