I have rc signal lost issue with my dji phantom 3 4K how to solve it

Note - when upgraded firmware a number of problems can present themselves - especially if you've traveled with the P3 (vibration, etc.).
If you get various errors such as weak image transmission signal, etc - first order of business is to completely delete and reinstall the DJI GO app from your device.
After that you'll want to place your P3 on a very level surface and do an IMU calibration.
It's always good to do a compass calibration before flying again.

Hello, if the app is always saying "No signal"  and the RC indicator is solid red, I'd suggest you to relink the RC and the drone. If this issue happens during the flight, please adjust the orientation of RC and antenna by following this video:

Hi, how far does it fly when it loses signal? Are you flying in an open field?