Steps to reproduce:
1. Open the attached "IN-93249" project
2. Open the "Main" Scene and enter Play mode
3. Move the character to the right until you reach a staircase
4. In the Hierarchy select Main → Lights → Crypt → Light Group - Entrance - 1 → Light Entrance GameObject
5. Change Overlap Operation from "additive" to "Alpha Blend"
6. Move the character around the entrance
7. Observe the Game view

Expected result: Light shines consistently
Actual result: Light turns on and off depending on your position near the entrance

Reproducible in : 2022.3.57f1, 6000.0.37f1, 6000.1.0b5, 6000.2.0a1

Reproducible on: Windows 11
Not reproducible on: No other environment tested

Note: Reproducible in Scene view as well