Duplicated Avatars cannot be added to Rig Source

Reproduction steps:

1. Open the attached project from Google Drive
2. Duplicate “GirlAvatar” from Assets folder
3. Select “vampire” model from Assets folder
4. In the Inspector add duplicated “GirlAvatar” avatar to Rig > Source

Expected result: Duplicated “GirlAvatar” is added to Source
Actual result: No Avatar is added

Reproduced with: 2021.3.30f1, 2022.1.0a5
Not reproduced with: 2022.3.10f1, 2023.1.14f1, 2023.2.0b10, 2023.3.0a6
Fixed in: 2022.1.0a6

Reproducible on: Windows 10
Not reproducible on: No other environment tested