When editing an object the shape tool window disappeared

Reproducible steps

1 - Open unity 19.3 import probuilder and the 4 samples
2 - Go to "tools" - "probuilder" - "pro builder window"
3 - Press the + next to new shape on the top left
4 - Change the shape to stairs - using the drop down shape selector
5 - In "curvature" go to the right where you can change the values and enter any number above 1
6 - Press enter

Actual Result:
The shape tool window has disappeared

Expected Result:
The shape tool window to stay where it is an not disappear until I close it.

Reproducible in:
2019.3.0a12 - 2018.1.9f2.

Device:
Tested on Windows

Note:
This only happens with the stairs and the sphere