We had a scene that was flown during the night time. One item was removed from the scene and we waited about 2 more hours until after sunrise and flew the scene again. An ortho was created for each flight and then the photos were combined for a third ortho. The night and day orthos look great. When they were combined there were small areas that displayed nothing. Specifically on top of a vehicle that had not been moved, etc. None of the images have any of these areas displayed. Looking for direction or suggestions on this. We haven not generally flown at different times of light and combined the images, but in this case it would have been beneficial. Any thoughts would be helpful.