How to reproduce:
1. Open the “UIToolkitBugsBundle.zip“ project
2. Open the “UIDocument.uxml” in UI Builder
3. Expand all USS files in the StyleSheets section
4. Duplicate the very first selector in the “1class.uss” file
5. Collapse all but the first USS file in the StyleSheets section
6. Delete the duplicated selector
7. Observe the StyleSheets Section

Expected result: All, except the first, USS files are collapsed
Actual result: All USS files are expanded

Reproducible in: 2022.1.0a1, 2022.3.62f1, 6000.0.49f1, 6000.1.3f1, 6000.2.0b1

Reproduced on: Windows 11 Pro (24H2)
Not reproduced on: No other environment tested