Those lines are showing you the areas that are overexposed. If you don't want to see them, disable the "Over Exposure Warning" setting in the following section of DJI GO:
@msinger thx for the input. By coincidences, I had the same experience today. The over exposure was a carry over from the other night when I had the camera tuned for the dark.
At first, I thought the B&W stripes were from something wrong with the drone or controller. Upon first power up, the Go App said there was an issue with the firmware -- I suspect with the mavic battery. It was unusually hot and humid today, and the battery wasnt quite fitting and locking properly. A power-down (drone, controller, phone), remount of the battery, and a full restart resolved the FW warning, but B&W stripes persisted.
If I get chance to get the magic up tomorrow, I'll check the OEW setting.