Today I was able to gain access and permission to film at the Carrie Furnaces, a Pittsburgh historical landmark which is comprised of two idled steel blast furnaces. The minute I get on property my Phantom 3 Pro starts generating compass errors. I knew I was close to large steel structures so I drove away from the site to try takeoff there. Same issue. Even indoors at the site today my bird would not take off due to the constant compass errors. I know the ground contains ferris material and the structures probably generate some interference, but what the hell? I did the firmware upgrade last week and have had several spectacular flights with zero incidences. I have noticed a few compass references on the threads but until today this hasn't affected me. I managed a few shots at the furnaces but nothing scares me more than that red compass warning coming up. Help!