Hmmm - are these black and white lines on the phone / tablet screen or in the video recorded onto the SD card?
If it's on the viewer, it probably is the over exposure warning that you can turn on / off in settings. If it's in the recorded video, try changing your SD card to a spare one and see if that makes a difference.
Agreed if they appear on the Go app, but I don't believe Litchi uses or has access to the overexposure lines.