How to reproduce:
1. Open user-submitted project (renderBug.zip)
2. Open the SampleScene
3. Make sure that Assets/Settings/ForwardRenderer contains a NewTestRenderFeature
4. Select the Reflection Probe in the Hierarchy window
5. In the Inspector window select 'Bake'
6. See the Reflection Probe preview

Expected result: preview of Reflection Probe Cubemap has the entire skybox
Actual result: part of the skybox in the Reflection Probe Cubemap is culled

Reproducible with Unity versions: 2019.3.6f1, 2020.1.0b1, 2020.2.0a3
Could not test with Unity versions: 2017.4.37f1(LWRP/URP unavailable), 2018.4.17f(unable to create a Forward Renderer with package versions available)

Reproducible with Universal RP versions: 5.7.2, 7.2.1
Could not test with Universal RP versions: 4.10.0 (unable to create a Forward Renderer)

Note:
Using RenderPassEvent.BeforeRenderingPrepasses does not cause this issue