Before / after drag slider ↔️

The bug not related to the core library. This custom style:

#beforeafter {
  width: 800px;
  max-width: 100%;
  margin: 0 auto;
}

800px fixed width create horizontal scroll on mobile.
Not related specifically to before/after plugin - even for empty div => not responsive.
Use the core library CSS

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/mhayes-twentytwenty/1.0.0/css/twentytwenty.min.css" />

Common Ninja Before and After plugin can be easily implemented into a Webflow site.
Before and After Plugin

Just following to check if this worked?