Getting focus/hardware input in a 3D widget (UE4.23.1)

I’m retro-fitting mouse input into a project but am having troubles getting buttons to register.

I have widgets setup in the world as part of a camera pawn (I can’t “add them to screen” for reasons, so they exist in the 3D world) but no matter what I do I can’t get button clicks/hovers/unhovers to work unless the widget is the closest to the camera with no other widgets in front of it.

In the setup above, the green widget has a button on it. As it has some other widgets overlaid (top image) the button doesn’t get any input.
Only when it’s at the front (bottom image) does that button register hardware input. Widgets blue and red are both set to “Receive hardware input FALSE”, “Window focusable FALSE” and "Window Visibility “SELF HIT TEST INVISIBLE”.

How can I get the button to register properly while it’s at the back / has other 3D widgets overlaid?
And no, I can’t move it to the front. :frowning:

Heh, maybe I figured it out.
I can set the overlaying widgets as “No collision” in the collision settings, which seems to do the trick, but will mean some collision activation juggling…