Seems that a recent update may have messed up Phantom 3's. I used to have no problem linking between my 3 4k and the controller. I went to fly it this past weekend and it just kept bouncing between connected and bad signal, and this was with me standing within 6 feet of the drone.
When I see people asking about do I need to get the latest firmware update it's like a 50/50 thing of what to tell them. You may be getting an enhancement that will improve usage, or you may be getting an update that degrades an otherwise working drone.
And I know it's not the area because I also have an MM and that has no connection issues between the drone and the controller.
Well that's my observation, if there is a way to get back to flying my Phantom 3 without having connection issues I would love to learn how.