That’s a good question. I’ve had the same problem over water. What model are you flying and what is your processing software? I fly with the P4 RTK and the RTK-2 base station and use Pix4D for processing. With the sub-inch location precision it does really well with processing photos with a lot of water, but does have problems when the picture is all water.
All I can figure to try is to fly further away from building so it pick up more features in a picture?
Is there subtle detail on the building walls?
How was the exposure in the individual images?
If over-exposed and there is some detail to work with, you might get better results in different light and/or slightly underexposing.