onPositionChange, onEnter and onLeave fire once on page load, and won't fire again until reload

I am using Waypoint to track whether a header has left the top of the viewport.

When a page is loaded (using Gatsbyjs's wrapper for react-router's `Link` component) `onPositionChange`, `onEnter` and `onLeave` are all fired at once (checked by using them to log a string to console), and then are never fired again when the page is scrolled. They are only fired again when I navigate to a different page, and they all fire at once again and the process repeats.

The `debug` output shows that waypoints of the child `div` are being tracked, and correctly identify when the `div` has left the viewport.

Despite this, none of the functions are triggering on scroll - I'm not sure if this is connected to react-router similar to #249