I have same display issue with the macbook pro 15 inch late 2016. In addition, I have also have had Keyboard issue. Apparently, the up arrow is not working properly. Today I have submitted the Mac at the Authorised service centre for keyboard replacement. At the service center, I have explained my display horizontal issue to an enginner. I was wonder when he said that he knew about horizontal line display issue.He also said that many users have complained about display issue. Sadly there is no solution for that. Eventually, I contacted to Apple support and explain the issues. Apple support have told me that Keyboard issue will be fixed however display will be fixed after the diagnosis. I am waiting for diagnosis report. I shall get within 7 days.
I will update the diagnosis report.
Please sign this petition
https://www.change.org/p/apple-fix-all-macbook-pro-2016-and-later-with-stage-light-effect-or-backlight-shutdown-flexgate