On mobile, if you catch the thumb while scrolling the content area, the two interactions counteract each other (scroll on content tries to scroll down while thumb tries to scroll up) which causes unexpected UI issues.

We should probably prevent the scrollbar from accepting pointer events if the scroll was initiated from the content area, or only trigger thumb scroll via a long press on the thumb (iOS appears to do something like this for native scrollbars).

In the following video, I'm scrolling the content area while touching close to the scrollbar. It's easier to reproduce here because the thumb has a pseudo-element that makes its hit area larger: