Thank you Wishgranter for the help!
I started go through the EXIF information of the pictures and noticed that something was not right with the GPS-coordinates. There are over 40 m big errors in the Z-coordinates and all of them had a negative value (minus prefix). I don’t have a clue why the Phantom 4 saves the elevation with a negative value.
So basically I need to remove the absolute position from most of the cameras. Is there by the way a cleaver way in how to evaluate the precision of the coordinates in the EXIF?
Best regards Gustav