Reproduction steps:
1. Open the attached “IN-77428_Deferred Lighting Bug.zip“ project (the link is in the internal comments)
2. Open the “SampleScene“
3. Observe the Game view

Expected result: “Spot Light” reflection looks like a full circle on the “Terrain” and Terrain Layers to the left and right of the Game view appear similar in brightness
Actual result: “Spot Light” reflection appears only on the left Terrain Layer (“Mud 2”) and the right Terrain Layer (“Forest 2”) is very dark (including the area where the two Terrain Layers are blended)

Reproducible with: 2021.3.43f1, 2022.3.44f1, 6000.0.17f1

Reproduced on: Windows 11 Pro (23H2)
Not reproduced on: No other environment tested

Notes:
- Could not reproduce in a new project (“Screen Space Ambient Occlusion” Renderer Feature seems to darken Terrain Layers 5 and above but not as much as in the user’s project and, in the user’s project, the “Screen Space Ambient Occlusion” Renderer Feature is not necessary to reproduce the issue)
- Reproducible in the Player
- Forward and Forward+ Rendering Paths produce expected results
- The “Global Illumination” Lighting feature is rendered even when using the Deferred Rendering Path (tested using Rendering Debugger window > Lighting > Lighting Debug Modes > Lighting Features)