I've posted this elsewhere but think I need to add here as well.
Just wanted to add my 2 cents worth (make that AU$800 worth).  I recently bought the latest ipad (6th gen) cellular so that I could have the GPS functionality because I specifically wanted to be able to use the 'my location' for the return to home when on a boat (mostly) only to find that I get the dreaded 'GPS signal too weak' issue making it useless for that function.
I don't understand why there is the 'button' to set this ability but it simply doesn't work for a large section of the drone community which is evident in many forums!  If you do a search on the subject there seems to be an endless trail of complaints about this very thing?!
The closest 'excuse' that I'm reading is that it's an accuracy thing - something about >10m that throws up the error.... so what!   If you are on a boat and lose sight of the drone or whatever and the Return to Controller function works then 10 m is nothing if it means getting the drone within 10 m of the new 'home point' where you could take control and land safely.
What have I missed here??!  Seems like an App issue to me!  Am I wrong?
Something else has now come to mind.  Does the new DJI '
Smart Controller' have this issue?  My new ipad and the 
Smart Controller both have GPS and GLONASS.  I wonder if the DJI product 'suffers' from the same problem?!
Anyone out there have one to check/test?