Volumetric cells issue

No matter how much I move the lightmass importance volumes I have an issue in a couple of rooms on my level where it wont place those little black cells in the volumetric lightmap, it acts like its an unimportant space. Ive tried faking some walls but no change. Ive baked lighting a dozen times and tried changes, current settings are 100 on detail cell size. would baking as sparse VLM improve things?

Update, baking it as Sparse changed nothing, still only limited cells in certain rooms

Update, baking it as Sparse changed nothing, still only limited cells in certain rooms

Update, baking it as Sparse changed nothing, still only limited cells in certain rooms