XPS 15 9530 Flickering horizontal bands on screen

There was another thread about this problem. I added a comment to that thread but got no reply. So, I'll try a fresh thread.

There are three flickering horizontal lines began on the screen.  They are transparent, a little less than 1cm in height and traverse the whole width of the screen.  Each line is separated from the next by about a quarter of the screen height.  There are three of them currently and they always appear at the same height on the screen.  They are barely noticeable on a white background but can be prominent and annoying on dark backgrounds or photos etc.

There were replies on that other thread that suggested several diagnostic tests. I performed those tests and here are the results.

Safe Mode: STILL VISIBLE

External Monitor: NOT VISIBLE

LCD BIST: Visible on the gray screen only

From reading through the rest of this thread, these results seem to indicate a screen problem rather than a software or system board problem.

My laptop is still under warranty. How can I get this fixed?