This is a bug report from Elliot:

As an Owner, I was trying to demote another user back to member. I clicked the dropdown and went “wat? Where’s the member?”. I then unselected owner and figured out what the deal was. Now I understand what you were going for here, and it’s clever: by having checkboxes, I can select multiple roles. Unfortunately, the way it’s implemented made it unclear how to go back to a normal user. I also don’t know from here if an auditor has more or less permissions than a member

Adding auditor to role breaks the “sorting”