I've noticed that sometimes I'm seeing surfaces (always floors/ceilings as far as I have noticed) showing the wrong lighting level. I *think* it might be something to do with updating of lighting information.
Examples:

Sector 1 has light level 112. Sector 2 is set at 120 and the adjacent sectors are progressively brighter. The walls look correct, but the ceiling doesn't. The only weird thing here is that the sectors are "flickered" by a script. The brightness of all sectors in the shot apart from 1 is lowered by a random value (never more than 8 - so it never goes darker than sector 2) and then set back to what it was originally.

This one is simpler. By the time this shot was taken, the slightly darker rectangle (sector 1) should look exactly the same as the surrounding sector 2. Both sectors are set up identically, except that sector 2 is secret and sector 1 has a tag.