Steps to reproduce:
1. Open the provided project "case_1203685-Level_Designing.zip"
2. In the Probuilder toolbar select "New Poly Shape"
3. Click in the Scene view to add an anchor point to start drawing

Expected results: an anchor point is added to the Scene view and the custom Poly Shape can be drawn
Actual results: an anchor point is not added to the Scene view and the custom Poly Shape cannot be drawn

Reproducible with: Probuilder 4.1.0 (2019.3.0b6, 2019.3.0f2, 2020.1.0a16)
Not reproducible with: Probuilder 4.0.2 (2018.4.14f1, 2019.2.16f1), Probuilder 4.1.0 (2019.3.0b5)
Could not test with 2017.4.35f1 due to package related errors

Note:
-Resetting the Layout to default lets you draw a New Poly Shape