I have flown my DJI Phantom 3 Pro for over 5 months, maximum range with the 3d printed parabolic reflector is 4km. I could have flown further but couldn't due to not enough battery. Last few weeks, I couldn't even flew pass 900m without getting Video Signal Weak warning and screen turned black. Flew at different locations is same. Finally I unscrew the optical sensor, underneath the circuit board there are four antennae connectors. They look pretty tight. But I took them out and put them back on. Added hot glue on them just enough so I can remove the glue later without too much difficulties. That solves the problem. So just want to report this so anyway can try this if they have similar issues. P.S. no need to remove the top shell. BTW I have a gimbal irratic movement issue. I had that for many months. This started to happen when I didn't fly it for a month. I tried put magnet close the compass and did imu calibration. That reduced the problem but does not solve it completely. I tried IMU calibration from the fridge but didn't work. If anyway can help me that would be great!