Probably an ID-10-T error, but Cut to Parts is acting weird for me

I’m working on a catch for a blow molded case and I would like to split it in a particular way to allow for easier installation and reassembly (if you’ve ever tried to install one of these, you know what I mean).

The problem I’m having is that when I move one of the sections from Part 2 to Part 1, the other section becomes a new object when I perform the cut - despite Cut to Parts being checked. When I leave the selection as-is, I get a single object with 2 parts. The modified selection gives me 2 objects.

What the heck am I doing wrong or did I discover a hidden Studio “feature”? Pics of what I’m seeing. First pic is the initial cut plane results, second is the results after the cut. Third is the cut I -want- to make, fourth is the results of that cut.

You need two planar cuts, one after the other, to accomplish that. Once you have it in 4 parts, you should be able to reassemble 3 of them together and split the 1 out.

Or a negative part, boolean combines, and a copy done with the opposite boolean.