Booleon Modifier Artifacts I'm trying to perform a booleon difference but I'm left with some odd geometry that I cannot seem to get to work correctly.

I've tried all the things I know about trying. On the objects I'm using as the cut out I have done a Clean Up -> Merge By Distance, and a Recalculation to ensure all the normals are facing in the right:



But I'm still left with this odd Geometry as an artifact of the booleon and I don't know what to do to fix it.



If I apply the booleon I end up with a really unexpected set of geometry that looks like this:



What do I need to do to eliminate this artifact in the resulting cut out? I'm using 2.81.

blend file
One thing that really improves Booleans is the 3D printing tool add one. Enable that (it is not enabled by default in 2.81) and then view it from the side menu at the top right. You can e it to check that everything is manifold and all your normals are correct and so one before you do a Boolean