Strange Artifact under SingleLayerWater with dynamic directional light and LightPropagationVolumes

upd. Regression was checked on //UE4/Release-4.26 CL 15973114, the issue was reproduced. Regression - No

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1. Create a new project
2. Enable the Water Plugin in the project
3. Enable Light Propagation Volumes in the project
4. Restart the editor
5. In the Content Browser's view options, enable Engine Content and Plugin Content
6. Open WaterContent\Maps\WaterTestMap
7. Select the directional light, and change its mobility to Movable, and its Dynamic Shadow Distance Movable to 80000
8. Observe black rectangular spot seemingly under the surface of the water that moves with the camera, and changes shape as the directional light is rotated.