Unity Sprite Editor sometimes 'attaches' a new slice to a previous slice - why?

Hi, this one is hard to explain but it's made using the Sprite Editor super frustrating since I updated Unity a couple of months ago. Updating it more over time hasn't helped (I'm on version 2019.3.13f1 right now).

I don't want to show the sprites from my actual game, so I've just drawn stick people as examples.

Let's say I've made a slice on Stickman 1 and named it 'Stick1', like so: https://imgur.com/3XVvsja

Next, I want to make a new slice on Stickman 2 and call it Stick2. But when I make that slice, it's automatically named Stick1 and is 'part' of the first slice I made, like so: https://imgur.com/xn9TQjh

As you can see, the box around Stickman 2 is green. Renaming it renames both slices, like the green one is a child or parent of the blue one. Now here's the weirdest part...

If I try to move the green box by clicking and dragging it, it's actually the BLUE box that moves, like the green box is the central nervous system and the blue box is the body. Like here, when I tried to move the green box down: https://imgur.com/3e6mR8j

This only happens sometimes, and I can't figure out what the conditions for it happening are. I couldn't find anything about it online, either. But I just want to be able to make a new slice every time, never have the slices joined to each other like this.

Anyone know what's going on? Thanks