Sometimes I get the strong interference warnings but when I just power down then turn it back on I then get no warnings for the rest of the flight. Even near large metal objects like wind turbines ( I keep my distance so I don't hit them ) or large flood lights.hope this helps and safe flying!

Go to phantomhelp.com they have every firmware for your phantoms I had the same problem Dji swore the firmware wasn’t the issue then they wanted me to send it in to be fix aaaa no so then I looked an found that site I downgrade firmware an wala it worked not more interference message so goes to show that theres a reason or hidden reasoning why they don’t want you to downgrade but saved money an my patience

I get that warning all the time, I usually just ignore it because I know it is probably just because of nearby cars, metal objects, ect. Although I have learned that if you are to close to a large amount of metal (like a car) then the compass calibration will fail.