Unity Muse Animate - Cannot Preview Animations / ‘GameObject can only be in one layer’ Error

Issue:

Muse Animate throws repeated errors in the Console:

A game object can only be in one layer. The layer needs to be in the range [0…31]
HandlesUtils.cs:29
PosingView.cs:64
PoseAuthoringLogic.cs:956
StageModel.cs:629

As a result, I can’t preview animations using the “Sample” button. The preview stays blank.

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