Quality report has red warning signs in reflectance target

Red warning signs appeared in Reflectance target column of Quality Report after running DSM, Ortho and Index. Not sure why as calibration was set in index calculator with no errors noted. This project is a combination of two flights, I used calibration photos from the first flight and from the second flight (40 minutes later) assigned to their respective groups. What does the red warning sign mean and how can I fix it?