As the select options appear in the #top-layer, this means that customisable select options appear above a position fixed navbar. If the user say opens a customizable select, then scrolls the page so the navbar and select options overlap. This is an issue for customizable selects as scrolling the page does not remove focus, unlike standard selects.

This seems to be an unfortunate side effect of using #top-layer, and as a developer I see two options:

1. Just tolerate it.
2. Implement a way to remove the options from the #top-layer when a scroll event occurs.

Regarding option 2 I implemented a solution using event listeners and DOM manipulation. This works, but it's rather unwieldy. An equivalent to hidePopover() for customisable selects would be useful here.