Reproduction steps:
1. Open attached Project "RenderIssue"
2. Open "Assets/Scenes/SampleScene" scene
3. Move the Scene View around the Quad
Or
1. Create an HDRP Project
2. Create a Quad and position it so that it blocks the view of a Decal
3. Create a Render Texture and set it as the Output of a Camera
4. Add the Render Texture to the Quad

Expected result: The Quad continues to block the view of Light Reflections
Actual result: The Light Reflections can be seen through the Quad until the Material is selected

Reproducible with: 10.0.0-preview.27, 10.1.0, 10.2.0 (2020.2.0b13, 2021.1.0a7)
Not reproducible with: 7.5.1, 8.0.1, 8.3.1 (2019.4.15f1, 2020.1.14f1)

Notes: Sometimes happens with non Render Texture Materials when importing an FBX Model
Only reproduces on HDRP, doesn't reproduce on URP