75% works when there are not a lot of trees involved. Your area was ALL trees so you really need to use 80+% to get it to turn out. There isn't much you can do to fix this after the fact without reflying the area.
When flying over trees make sure that the shadow of the aircraft is not falling within the field of view of the camera. If it does, it leads to a sun hotspot that moves with the aircraft which is essentially changing how each figure looks in each image. This is bad for feature matching and leads to failures. Just something else to look out for when recollecting your data.