I’ve had this problem a few times and still can’t seem to work out a way around it without disabling cast shadows altogether. It usually happens when I have two doors side-by-side in a scene, such as a fridge or wardrobe doors.
This is what I want it to look like (mobility: static):
Visualizing the volume sample placement and seeing if the top mesh is out of range of the placed sample that is lighting the one below would be a good place to start. You can quickly check this by taking the door and moving it down closer to the floor like the bottom door and see if the lighting is similar between the two then. If so, you’ll want to adjust the height or number of samples that is placed. This may have to be done in the BaseLightmass.ini file to get the best results, but you should be able to get it in the editor without having to touch the ini file.
I managed to find both the in-editor settings and then relevant .ini settings under [DevOptions.PrecomputedDynamicObjectLighting], but after about half an hour of trying a number of different height, spacing and sample layer settings I’ve made no progress. Am I missing something?