ok i remember seeing this little ribbon conenctor on the side of the gimbal board which is put there for servicing by dji, in this picture here taken from another forum you can clearly see it. I do notice tx and rx pads, and 3v3 pads and gnd pads on the gimbal board, and the unused ribbon connector that is circled is probably used for this exact procedure. however, we run into a problem. first, there is no way for us to get ahold of a ribbon cable that hooks up to this connector. second, if we were to use an ftdi adapter (like the man does in the p2 repair you mention) we will need mavic pro specific flash files. That is all considering that my theory is correct and the nand chip is actually located on the gimbal board and not the core board of the mavic pro. I will check into a github page which i used to read a long time ago from a member called mephistoteles, he had done a lot of work and reverse engineering on the p3. lets hope i will find something that is helpful for the mavic pro. Btw, i wanted to ask you, did you try replacing the actual camera module? i am waiting on a "bad" one that wont focus from a friend who just shipped it to me. If it turns out that i still get black image then our problem is down to the gimbal board, or the core board and your nand chip theory is going to gain much more ground. I will keep in touch, lets hope we can fix this