Lightmap Density view - Grid not showing on some meshes

When I turn on Lightmap Density mode in the viewport for some reason the grid isn’t showing on some of my meshes. Any idea how to fix this?

In the image you can see I have a door mesh selected but it’s not showing the grid on it or the adjacent walls or the floor.

they only show after rebuilding lighting.
Which is the most common reason for ^ that to happen.

Yeah this is after rebuilding lighting but I think the problem is with the map file itself. When I rebuild the lighting the lightmap resolution of these meshes looks to be around 16 even though they’re both set to 128. I threw the meshes into a clean map and rebuilt the lighting and it looks fine so I think I have to re-do my map sadly.

Thanks for the reply!