I'm a photographer and have been testing the cameras on my Mavic 4 while using Active Track. Testing the limits is always a good learning experience. Here all these 3 pics(shot RAW) were photographed at 1/8th sec using a ND64. Once the drone...
It can be something as simple as a bright point of light well off camera axis that has been caught and refracted onto the sensor which has dutifully recorded it.