After DJI Phantom 3 std was returned "repaired" in 3 weeks, I now only have the same signal loss issue I sent it to them for, I also have a dark pic.

If I put my hand in front of the camera, and move it, it's a perfect pic for about 10 seconds, then graudually gets darker and darker until it's 100% useless.

any ideas ? seems like some sort of auto-iris problem.

Fixed.....uninstalled litchi, djigo, reinstalled djigo, put all settings at default,  cam works fine.....

What is your ISO setting? If it's auto, it will  change the light according to the environment, if you cover the lens by hand, the screen will become darker and darker, if you set to a certain value, the screen will hold the same light condition.