IF you have a P3P/A, take a look at DJI-TIMs post HERE.
How are you setting your image transmission setting - Auto or Custom?
And are you reducing your transmission speed?
For longer range flights, you may want to select Custom with reduced speed:


With a P3S, take a look HERE.

I assume you are flying an advanced or pro correct ?  You may want to enable the "Enable Hardware decode " Under general settings ( Go App ) to take some of the burden off of the processor.  This may help.  I for one have never lost the video where it did not return.  What type of device are you using for go app?  I-pad....Phone...nexus ?  Perhaps enable airplane mode as well. Make sure you are using good antenna practices as well, make sure they dont cross etc.   

Some things to try  - let us know - donnie

What device are you using that showing the optional image transmission setting? I'm currently using a samsung S6 but no such option appear in DJI GO app. It is really necessary to have that kind of thing? Looking at the screenshot above, I think it is rather good to have that options..:

you might find a solution in this thread http://forum.dji.com/thread-39021-1-1.html