Runtime settings, composer settings & Collider settings dropdown list doesn't expand on clicking its Lable under the Preferences Cinemachine window, refer attached video.

Steps to repro:
1. Create a New Project
2. Package Manager > Cinemachine > Install
3. Edit > Preferences > Cinemachine > Click on Runtime setting Lable

Actual Result:
Dropdown doesn't expand on clicking its Lable

Expected Result:
Dropdown expand on clicking its Lable

Occurring on:
2020.2.0a19, 2020.2.0a5, 2020.1.0f1, 2020.1.0b6, 2019.4.6f1, 2018.4.25f1 with Package Version
2.6.0, 2.5.0

Working Fine on:
2020.2.0a4, 2020.1.0b5

Environment:
Occurring on Windows 10 & Mac 10.15.

Workaround: On clicking dropdown icon it expands.