Problem with volumetric lightmap

Hi everyone!
We are developing a VR project for an important Italian museum, and we’ve a problem with volumetric lightmap in UE4.19
In the upload attachments you can see a gap in volumetric lightmap also using “volumetric lightmap density” volume (with “allowed mip level range” set to Min=0,Max=0).
This causes a bad rendering of shadows on movable object near gap. The 2nd photo uploaded shows the settings of world lightmass, furthermore we followed the settings writed in page, setting “MinBrickError” to 0 in BaseLightmass.ini.
Could someone tell us if we wrong something or if it’s a bug?
Thank you very much for the help.