Repro steps:
1. Open attached project
2. Open Game view
3. Select "Area Light" in the Hierarchy
4. In the Light component, change the Shape parameter to Rectangle and wait for the scene to bake
5. In the Light component, change the Shape parameter to Disc and wait for the scene to bake

Expected result: Light is generated using both shapes
Actual result: Light is generated only using Rectangle shape

Reproducible with: 2018.4.6f1, 2019.1.14f1, 2019.2.1f1, 2019.3.0a12
Could not test with: 2017.4.31f1 (Lightweight RP package not available)

Reproducible with package versions: 4.0.0, 7.0.1
Not reproducible with package versions: 3.3.0

Note: Disc-shaped light is seen after updating the LWRP package to 5.7.2 or 7.0.1. It disappears after making changes to "Area Light".