Reproduction steps:
1. Open the attached project "case_1361819_Repro.7z"
2. Open Assets > SampleScene
3. Select "Bandit" GameObject and expand its hierarchy
4. Find and drag "head1_head" GameObject to Transforms property of Bone Renderer Component of "Bandit" GameObject
5. Find and drag "head1_neck" GameObject to Transforms property of Bone Renderer Component of "Bandit" GameObject

Expected results: All bones added to the Transforms property are visible in the Scene view
Actual Results: Not all bones added to the Transforms property are visible in the Scene view

Reproducible with: 1.0.2, 1.0.3, 1.1.0, 1.1.1 (2020.2.0a16, 2020.3.18f1, 2021.1.20f1, 2021.2.0b11, 2022.1.0a8)
Not reproducible with: 0.2.7-preview (2019.4.30f1), 0.3.2-preview, 0.3.3-preview, 0.3.4-preview (2020.2.0a15)

Notes:
- disabling and re-enabling the Bone Renderer component or expanding/collapsing Transforms property redraws the bones
- bones get rendered immediately when adding them to an existing element in Transforms
- first bone dragged into Transforms property after opening the scene gets rendered immediately

Animation Rigging Package regression in 1.0.2 and above versions, which are available in Unity 2020.2.0a16 and above