I have a mavic pro. whenever i get to around 500m the video being displayed on my iphone 7 gets grainy then cuts out completely. I still have full control from the RC and can send it home but it's strange that I can only get 500m when its advertised at 7km?

what I've tried:

iphone 7 is my old phone so I did a complete format with nothing but the go app. also set in airplane mode.
tried using in a large open field with no comms towers or trees.
tried using in a paddock with some trees and a comms tower.
my HD settings are all set to auto.
tried using an iOS cable from the underside of the controller.

still can't manage to get over 500m. any help?

Marksus, just to verify, the transmission only gets grainy when it goes to 500 meters away, right? May I know the firmware of your drone and RC? Please try to refresh the latest firmware for it to ensure the consistency. Also, check the antennas position of the remote controller, keep it placed correctly, please refer to the tutorial below. And if it doesn't help, please help to confirm if there is a crash or hard landing before, you can send the drone back and we will help to manage an overall check for the drone. Please contact support@dji.com for a further help.

THanks for the reply.

I adjusted the antennas just now and was able to get up to 1.2km.  Running the latest firmware on both the aircraft and RC. no crash or harsh landing. I'll try a completely flat and open field then see what kind of distance i can get. cheers