How to reproduce:
1. Open the attached project named "Case_1282153"
2. Open the SampleScene
3. Select the Shadow Caster 2 and click the "Edit Shape" button in the Inspector window
4. Drag on the scene view to create a rectangle selection box and try selecting some vertices

Expected result: Vertices that are inside the selection box are selected and highlighted
Actual result: Some vertices inside the selection box are not selected while other vertices that are outside the selection box are selected

Reproducible with: 8.0.1(2020.1.0a24), 8.2.0(2020.1.8f1), 9.0.0-preview.55(2020.2.0b6), 10.1.0(2020.2.0b6)
Not reproducible with: 7.5.1(2019.4.12f1), 8.0.1(2020.1.0a23)
Couldn't test with: 2018.4.28f1(URP was not yet available)