Boolean always substracting the wrong object

I am really struggeling with being able to make “Boolean operators” do what I want. Occasionally I have managed to get it done, but now not any more. My problem is that of multiple options which of both object to subtract from which Lightburn always seems to choose the wrong one, irrespective of the order I selce them or wether I use “A-B” or “B-A” in the “Boolean Operator” Menu.

So let’s say my objects are a Font over a shape. See here.

The desired outcome is this:

But whatever I do, I always end up like this:

(or with a totally blank shape). But whatever I do (A-B or B-A), the shape is always blank.
Obviously it also doesn’t help that there is ZERO option to preview in the [Ctrl-B] Boolean operator popup.
How is it possible that NEITHER A-B NO B-A leaves the shape filled? One of them BY DEFINITION should do that!?!
What am I doing wrong?