I can't fully explain what happened, but I did have a similar issue 2 months ago. I had vertical lines about the same length coming down from the top of the screen. I brought the car into the service center and they replaced the MCU. The text of my invoice is below. 2014 Model S.
Concern: Customer states the touchscreen has flickering black lines on the top. It appears
that the touchscreen may be going bad. Inspect/Advise.
Pay Type: Warranty
Corrections: Media Control Unit (Touchscreen)
Diagnostics show the media control unit is not functioning appropriately. Removed and
replaced the media control unit, pushed updated firmware to ensure proper
communication..
Part Quantity
MCU NA PREMIUM - Model S and Model X
(1045006-00-D)
1
ANTENNA , BLUETOOTH (1052393-00-B) 1
ASSY,HARN,MDLS,JUMPER, HSD CAMERA
(1127304-00-B)
1
Parts Replaced or Added
Corrections: Update Navigation Maps Using Toolbox
Technicians then updated the firmware on vehicle and maps for the navigation.