Hello,
If you turn on "Keep depth maps" option in the Preferences window you'll be able to see the cameras with the depth maps generated in the Photos pane (the icons in the thumbnail corner will appear after the dense cloud stage). So if you find the cameras without the depth maps you can open View Matches window to check whether there is sufficient number of matching points between the selected photo and other images. In case there are too few matching points between any pair of images, such pair is being assumed as non-overlapping.