Chrome Version       : 68.0.3409.2
OS Version: 10.0

I don't know what causes it (something about middle-clicking certain links?), but for many weeks now, Chrome has had a bug where mouse wheel scrolling stops working.

Interestingly, using middle-mouse autoscroll (by clicking the wheel and pulling down until the page starts to scroll; even a brief time is sufficient) and then existing from it causes wheel scrolls to start working again.

I wonder if somehow we think we're in autoscroll mode (and should suppress mouse wheel events) when we aren't.