Asset thumbnails flicker when UI Builder window is open containing a Visual Element with assigned Material

Steps to reproduce:

1. Open the attached project
2. Open the test.uxml asset in UI Builder
3. Assign Mat_UI_Shader.material to one of the Visual Elements
4. Move the mouse cursor around the screen and observe Asset thumbnails in the Project window

Actual results: Asset thumbnails in the Project window start flickering, especially when the mouse cursor is transitioning between the UI Builder window

Expected results: Having a UI Builder window open does not affect asset thumbnails in the Project window

Reproducible with versions: 6000.5.0a4

Not reproducible with versions: 6000.0.65f1, 6000.3.3f1, 6000.4.0b3, 6000.5.0a3

Tested on (OS): Ubuntu 24.04, macOS 26.1

Notes:

• The UI Builder window must be open, and at least one of the Visual Elements must have an assigned material for the issue to occur