USS will not update when removing selectors after saving changes once in StyleSheet Editing

Steps to reproduce:

1. Create and open a new project
2. Open 'Edit -> UI Toolkit -> Enable StyleSheet Editing Mode'
3. In Project, create and open 'UI Toolkit -> Style Sheet (USS)' in UI Builder
4. Expand the new USS file in UI Builder
5. Expand the USS Preview below the Viewport
6. Duplicate the 'VisualElement' selector in UI Builder's Hierarchy a few times
7. Save the changes
8. Delete one of the VisualElements
9. Observe the USS preview

Actual results: The same number of VisualElements is displayed (like in step 7)

Expected results: One less VisualElement is displayed

Reproducible with versions: 6000.7.0b1, 7000.0.0a1

Can’t test with versions: 6000.0.84f1, 6000.3.24f1, 6000.6.2f1, 6000.7.0a6 (No StyleSheet Editing preview)

Tested on (OS): Windows 11 Pro (25H2)

Notes:

• USS gets dirty, however saving does nothing - upon reopening UI Builder, the deleted elements return
• Adding elements still appends code to the USS
• After reproducing, any changes done to selectors are not registered in USS code/USS preview, but are displayed in UI Builder's Inspector
• Only reproducible when using the StyleSheet Editing in UI Builder