Thanks for testing.
You are using it exactly as intended, and your file works without changes on my current build:
I think what you are seeing is caused by a bug which resulted in some flipped normals in the output of the first Fuse, which then cause problems when it is passed to the next one.
I caught this just a bit too late to make it into this last Beta release, but the fix will be in the next one.
If you want to try a hotfix, it should work to just put this file in place of the existing one in your
Rhino WIP\Plug-ins\Grasshopper\Components directory:
Kangaroo2Component.gha (314 KB)
This shape is a good example of the kind of thing the tool should work well for - reasonably dense mesh, similar quad density on the parts where they meet, and simple intersections.
To manage people’s expectations though - Fuse will not work in many cases where the intersection is more complex (i.e. each fusion seam doesn’t form a single loop). Also large faces on one of the shapes that pass through multiple non-contiguous faces on the other will probably break it.
These things will likely be possible to improve somewhat, but this approach might not be possible to make ultra-robust for really complex booleans.
Also - the input is not required to be closed, though open shapes might behave less predictably, and the boundaries should not cross the parts where the 2 pieces join.