I was unable to drag/drop prefabs into my project window from scene view (with this certain project only) like before.

Steps:
1. Download the fontain demo from here: https://drive.google.com/open?id=1dqEWj99GeolmGglaYNVh8Hqm5AJY-5vO
2. Open the Sample forest scene
3. Try to drag and create a prefab group from "Rocks" parent object
4. Notice it will try and do something, but nothing will happen
5. Right click the asset and convert it to a prefab.
6. This will create a prefab however any objects with the HD Lit material will lose their materials - Layered Lit was okay.
7. restart the project to see the materials restored.

Image A: https://i.gyazo.com/29a672f602097c38b6c81d3b5193c40a.png
Image B: https://i.gyazo.com/0740f759a962b77b5e88b52990384557.png

See doc for more gifs: https://docs.google.com/document/d/1fakp98T1ecndQAe6lLMgXomFA_CSywckr1txMEw5U5A/edit?usp=sharing