Good idea. I'll go back and re-shoot that location with differing gimbal angles.
Looking at the alignment of the gimbal and the prop disks, I don't see how the props could ever shadow the lens directly. The light source would have to be nearly on the horizon.
I'm surprised that I haven't seen this on other Mini 3 footage. Backlight is popular.
I was unable to replicate the original conditions due to sun angle and time of day. I need to return once more to that location.
I was able to test in some severe backlit conditions and I can see that the Mini 3 lens is quite susceptible to internal reflections. These appear so far to be codec agnostic.
Might be time to investigate a small "french flag" (sun shade) for the lens. It could mount with velcro directly to the aircraft body and would weigh virtually zero.