Right-clicking a docked preview window leads to the Inspector Window properties being selected.
Refer to the attached video.

Steps to Reproduce:
1. Create a New Project
2. Hierarchy > Right-click > 3D object > Tree (basically any asset which has a preview)
3. Inspector > Preview Window > Resize
4. Right-click on the Preview window in different places

Actual Result:
Right-click carries through to the inspector window behind the preview window

Expected Result:
Right-click should target preview window

Occurring on:
2020.2.0a2, 2020.1.0b1, 2019.3.5f1, 2019.3.0b10

Working Fine on:
2019.3.0b9, 2019.2.21f1

Environment:
Only Windows 10