Nearby router/wireless things? Controller antennas down/out, not straight up? Was it continuous or sporadic? Did it stop right when you turned the microwave off?
Footage captured on the memory card wont show these artifacts. What you are seeing is interference in the stream from the broadcast feed from the phantom. This can be caused by nearby wifi, bluetooth or other electronic interference.
Footage captured on the memory card are ok. And you're right, controls close to home where I have wifi. Try to follow to your advice. Away from wifi signal and I see if the problem continues. Thanks for reply.