Volumetric lightmap cache point becomes extreme bright if the light source is accidently at the exact(or almost) location of it

Project settings: allow static lighting; set up a simple level with some static meshes, one movable mesh(the groud mesh for example) and a static point light, built lighting by using CPU lightmass; Visualize the Volumetric lightmap in viewport; move the static light to one of the Volumetric lightmap cache point as close as possible; built lighting again; You will see that Volumetric lightmap sample close to the light is exteme bright as well as the ground mesh which lit by the cache.
This just happens in CPU lightmass. GPU Lightmass is fine
Up image(GPU), Down image(CPU) 

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