So all morning I have been working on a scene and baking lighting with no issues. I didn’t change any lighting or move any objects. I updated a few texture maps in the shaders and did a rebake and now I get huge black walls and looks like the light is not being baked correctly.
That’s certainly not normal. You may want to try the “Validate” cache option. Or as a more drastic resort, possibly even locating your SwarmCache in Windows and deleting the contents of the sub-folders (the link I provided explains how to locate it).
I have the same problem on my computer (i7-7800X - 32GO ram) with a scene. Same effect (black faces on some meshes) appear each time I build lighting. But on another computer, the problem doesn’t seem to appear, with the same scene and lightbuilding parameters. I tried to flush my cache, validate option and even deleting all caceh folder, nothing changed.