How to reproduce:
1. Open the attached project named "Repro_906066"
2. Open the "ReproPath" Scene
3. Select the "SumpLargePipe" gameObject in the Hierarchy
4. Click the Edit Path button in the Inspector window
5. Try selecting a few points using the box selection

Expected result: All the points inside the selection box ar selected
Actual result: The selection of the points is offset on the Y-axis

Reproducible with: 2019.4.11f1(2.0.6), 2020.1.8f1(3.0.2), 2020.2.0b3(4.0.1)
Could not test with: 2018.4.27f1(Project breaks upon downgrading)

Notes:
1. Selecting multiple points using CTRL+Left-Click works as expected