Problem
Overlays in prototypes are additive and continue to add layers on top.
This becomes apparent when the prototype flow moves from one overlay to another.
If the ‘close when clicking outside’ and ‘add background behind overlay’ are selected, the background will continue to darken even if the flow is only switching between two frames. Clicking outside the overlay will remove each, one-by-one instead of the desired result of dismissing the overlay completely.