If you create a material preset and select it in the Project View, the preview icon in the Inspector will flash.

1. Install Unity
2. Open the attached project
3. Open SampleScene.scene
4. Select Material.preset in the Assets folder
5. Look at the material icon in the Inspector

Expected Result:
Preview icon accurately reflects the material preset.

Actual Result:
The preview icon flashes.

Regression introduced in 2018.3.0b7

Tested on MacOS and Windows, but can only reproduce on Windows.

Reproduces On 2018.3.0b7, 2018.3.0b10, 2019.1.0a9

Doesn't Reproduce On 2018.3.0a6