Thanks for the positive feedback. I posted on the PX4 google group to hopefully get some good feedback from that community as well. I did email DJI, but as dazzab suggested, there's little hope of getting a useful reply.
I’m working on a study to understand the most common sources of bugs in drone software. I’d love to hear from developers about where bugs commonly arise. Here is a certainly non-exhaustive list of potential sources of problems:
Mathematical mistakes in control laws
Control implementation bugs...