Still no fix yet? A pic of the fuse box under the dash and the fuse might be helpful to us with this problem.
*** Update/Solved***
After doing an intensive lamp-by-lamp uninstall and still being left with problems mentioned earlier in this thread I looked for a more logical answer and found it!
On the 2008 Tahoe or similar I'm guessing - Pop open the Interior Fuse Box on the left side of the drivers side dash - Locate Fuse #17 - Labeled "IS LPS" which is a Red 10A fuse towards the right side - Check for blown fuse, If so there should be a spare attached to the fuse door panel
This was a lucky desperation find, never really suspected a fuse since all the lighting worked in one way or another, just abnormally, but sure enough this interior lamp fuse was blown and once replace all the lighting works as it should in auto and manual settings.
Hope this helps other as this issue took months to resolve with no searchable solutions to be found online anywhere... will repost in my dedicated thread to spread the knowledge!