I believe that UFO stands for Unidentified Flying Object....
Having spent a lot of time photographing in very poor light, often an object will appear on film as an aberration due to light being transmitted into the camera,( hence the use of lens shades) but hitting the side of the lens prior to landing on the sensor. A automatic lens will by definition open up to the maximum in poor light as well as the shutter speed will be longer, both or either, can influence what the camera records. Even when using my Nikon D750 at max aperture F1 and a speed of 1-2 seconds I have to wind up my film speed well over 2800ASA, I can still get "ghosts" especially if a relatively bright subject appears slightly off focus. DJI lenses though good, are no way near the quality of a DSLR (even the "Hasselblad" lenses looking at the spec's.
The problem is not unusual, but is a pain when it happens.