Reproduction steps:
1. Create a new 3D project
2. Open the Package Manager window (Window > Package Manager)
3. Install package by name: “com.unity.muse.behavior”
4. Observe the console
OR
1. Create a new 3D project
2. Open the Package Manager window (Window > Package Manager)
3. Install package by name: “com.unity.muse.behavior”
4. Right-click on “Packages” in the Project window
5. Select the “Reimport All” option
6. After the Editor is restarted observe the console

Expected result: No errors are printed out
Actual result: Error regarding UI Toolkit Source Generator are printed out: {{Unity.UIToolkit.SourceGenerator\Unity.UIToolkit.SourceGenerator.UxmlSerializedDataGenerator\Unity.AppUI.UI.AccordionItem.gen.cs(11,14): error CS1729: 'HeaderAttribute' does not contain a constructor that takes 2 arguments}}

Reproducible with: 6000.0.0b13, 6000.0.5f1
Not reproducible with: 2021.3.39f1, 2022.3.32f1, 6000.0.0b12

Reproducible on: Windows 10, Windows 11 (user)
Not reproducible on: No other environment tested

Notes:
- If the reproduction is not successful, try deleting the “Library” folder after installing the “Muse Behavior” package
- The reproduction is not consistent