The flight lines seem to indicate that you have plenty of overlap in your photos. There are plenty of shadows however, which could affect your results if your camera doesn't have adequate dynamic range (i.e. ability to distinguish slight variations in color, especially in shadowy areas).
Are you using the latest version, which is Drone2Map 1.1? Would you be able to provide your data if I gave you an upload location? Assuming you have tried this with version 1.1, we would be willing to give it a go.