How to reproduce:
1) Create a new project
2) Window > Package Manager > Install Probuilder
3) Probuilder > New Shape > Draw Shape
4) Draw Shape > Select Snapping, Settings Options

Expected result: No errors are thrown when interacting with settings in the 'Draw Shape' window.
Actual result: Errors are thrown when interacting with settings in the 'Draw Shape' window.

Reproducible with: 2021.1.0a8(5.0.0-pre.7)
Not reproducible with: 2019.4.14f1, 2020.1.12f1, 2020.2.0b14(5.0.0-pre.7)
Could not test with: 2021.1.0a1, 2021.1.0a7(Probuilder package version 5.0.0-pre.7 was not available)

Notes:
1. Reproducible with Windows10 and macOS 10.15
2. While creating New Shape, when interacting with settings in the 'Draw Shape' window, the following errors are thrown in the console.
- ArgumentException: An item with the same key has already been added.
- [Physics.PhysX] TriangleMesh::loadFromDesc: desc.isValid() failed!
- GUI Error: You are pushing more GUIClips than you are popping.