[2D][Sprite Editor] Safe or Smart slicing causes some sprite rects to become parented or unselectable

After using safe or smart slice on some spritesheets, certain generated sprite rects become hard to select by mouse. After moving some rects and generating new ones, some newly generated ones become unselectable and clicking them causes other rects to be selected

Repro steps:
1. Open attached project and open Assets > Sprites > RetroSpaceship.png in Sprite Editor window
2. In Sprite Editor, select Slice dropdown > Method: Safe/Smart > Click "Slice" button
3. Try to move "RetroSpaceship_0/1/2" rects, notice difficulty in moving especially when dragging from top half of rect
4. Rename "RetroSpaceship_3" into "b1", "RetroSpaceship_10" into "b2"
5. Drag "b2" rect to an empty spot on spritesheet
6. Redo Step 2 and observe new generated rect where "b2" was
7. Selecting newly generated rect causes b1 to be selected instead
Clicking "Apply" after causes warning in console:
Identifier uniqueness violation: 'Name:b2, Type:Sprite'. Multiple Objects with the same name/type are generated by this Importer. There is no guarantee that subsequent imports of this asset will properly re-link to these targets.
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&)

Expected result: Safe or smart slicing should not affect selection of generated sprite rects
Actual result: Safe or smart slicing causes generated sprite rects to become hard to select or unselectable

Issue found on: 2020.2.0a16, 2019.4.3f1