Reproduction steps:
1. Open the attached "IN-139024_MaterialPreviewBug.zip" project
2. In the Project window, select the "Material.mat" asset located in the "Assets" folder
3. In the Inspector, click the 3 dots located at the top right of the material preview window > "Convert to Floating Window"
4. Change the "Base Map" of the material to any noticeable color of your choice
5. Observe the floating Material preview window
Actual result: Material doesn't change its color
Expected result: Material changes its color
Reproducible with: 2023.2.0a19, 6000.0.72f1, 6000.3.13f1, 6000.4.2f1, 6000.5.0b3, 6000.6.0a2
Not reproducible with: 2023.2.0a18
Reproducible environment: Windows 11
Not reproducible environment: No other environments tested
Workaround: Hover over the floating preview window with the mouse to update the preview
Note: Issue reproduces in HDRP, URP, and SRP with their default materials respectively