How to reproduce:
1. Open the attached 'test-packages-2d.zip' project
2. Select Assets -> Test -> 'ExplosionSprite' Sprite
3. Open Sprite Editor
4. Select Slice menu in the control bar
5. Select Smart in the Method dropdown
6. Press the Slice button

Expected result: The bigger part of top-right Sprite is sliced alongside other parts of the Sprite
Actual result: The bigger part of top-right Sprite is not sliced and the below part of the Sprite is sliced twice

Reproducible with: 2017.4.33f1, 2018.4.12f1, 2019.2.11f1 (1.0.0), 2019.3.0b8 (1.0.0), 2020.1.0a9 (1.0.0)

Note: 2017.4, 2018.4 Sprite Editor is not included in the package