It is very common when mapping a large area that contains structures to forget to account for the added height of the building when planning for overlap.
When flying low, it is very easy to forget that areas that are above the ground will get less overlap due to the wide field of view of most aerial cameras.
If you are flying at 50 meters above ground level and there is a building that is 15 meters tall, you are going to have a bad time. This why the Data Collection guidelines recommend flying at least 4-5 times the height of the tallest object. The goal is to limit differences in coverage due to differences in height.
The example below shows the overlap being set around 70% so the coverage on the ground is good but the roofs of the structures in the middle get very little coverage. In the case of a shiny metal or featureless roof, this can make it hard to accurately reconstruct. The areas with only 4X overlap ended up being distorted with swirls.
Read more about the effect in the "Elevation Difference Overlap Reduction in Structures" section of the Overlap Reports article.
To keep this from happening, fly higher to limit this effect or use more overlap than is generally needed. Another way to fix this would be to take a few extra pictures to fill in the overlap and include that with the uploaded imagery.