Attempting to unlock Scatter with browser on external monitor, Scatter interface is blank / not visible

[acoutts]

MacBook Pro (Retina, 13-inch, Mid 2014)
macOS High Sierra 10.13.6

When Scatter is locked and I click on the Scatter icon while the browser window is on the external screen, the Scatter interface is blank:

The interface can still be interacted with if I click where the button on screen should be, but none of the UI is visible unless I drag the browser window back to my Macbook.

Once I unlock Scatter, I am able to see and interact with the Scatter interface as expected on the external screen.

[nsjames]

What. The. Fuck.

:)

I literally don't know what to say here. Peanut butter and jelly?
If you inspect the open popup and mess around with the CSS for what should be there, does anything help? ( display:block maybe? )