Reproduction steps:
1. Open the attached “Legs Mask Bug.zip” project
2. Open the “Assets/Scenes/SampleScene.unity“ Scene
3. Open the “Assets/Animations/Animation Controllers/Base Controller.controller” animator controller
4. Enter the Play Mode
5. Click the gear wheel on the right of the “Flying Legs” layer to show the settings for this layer
6. Change the Weight value to 1
7. Observe the Game view

Expected result: Legs are lifted up
Actual result: Legs remain stationary and are not lifted

Reproducible with: 2021.3.46f1, 2022.3.55f1, 6000.0.32f1, 6000.1.0a8

Reproducible on: Windows 11
Not reproducible on: No other environment tested