Reproduction steps:

1. Open "lighting-repro.zip" project and open "SampleScene" scene
2. Switch to one of the Repro Graphics APIs in the Player settings
3. Notice a change of lighting on the model (dark shadows)
4. Switch to "2 Bones" in "Blend Weights" in "Quality" settings or disable "GPU Skinning*"
5. Notice a change in lighting on the model (highlights)

Expected Result: "1 Bone" "Blend Weights" don't have unexpected shadows
Actual Result: "1 Bone" "Blend Weights" has unexpected shadows

Reproduced with: 2019.1.0a8, 2019.1.0a7, 2019.1.0a5, 2018.3.6f1, 2018.3.3f1, 2018.3.0f1, 2018.3.0b1, 2018.3.0a6, 2018.3.0a5,
Did not reproduce on: 2019.2.0a5, 2019.2.0a1, 2019.1.0b3, 2019.1.0a10, 2019.1.0a9, 2018.3.0a3, 2018.3.0a1, 2017.4.20f2 (Model is broken)

Repro Graphics API:
Direct3D12
Vulkan
Metal