- Dragging a scrollbar on a webpage causes the page to scroll in the opposite direction.
- The WebViewPrefab's Drag Mode is set to "Drag to Scroll".
By default, a WebViewPrefab's Drag Mode is set to Drag To Scroll, which causes all drag interactions to trigger mobile-like scrolling, as if the cursor is dragging the page. In this mode, individual elements within the page, including the scrollbar, cannot be dragged.
In order to be able to drag the scrollbar or other individual elements within a page, change the WebViewPrefab's Drag Mode to Drag Within Page.
See also: How can I hide scrollbars?