'Accessibility Contrast errors/ not accessible in smaller screen using AOS

I'm building a timeline effect using AOS https://github.com/michalsnik/aos . However, the element disappears

It would be really appreciated if you can help me:

What is the possible cause of this ? (So i can check the part by myself)
On their site: https://michalsnik.github.io/aos/ is still working fine on my phone, so I know it is something in my project conflicting?
It is really long file, if you want the source code of the project I will provide Github links if needed.

html css aos.js

Sources

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