Not the typical flex gate problem.Haven't found same problem with mine

Give this a try, restart the system and press the Shift (⇧) key to enter safe mode. Try using the system this way to see if the display reacts in the same way

Reference: Mac startup key combinations

I’m suspecting the T-CON board which typically sits within the display lid area has failed here. The retina displays have a higher scan frequency so it’s possible the clocking within the T-CON has failed but only the higher one. Running in Safe Mode we are keeping the system at the lower clock rate.

If that works I think that nails it as a T-CON issue.

So unless you can get to an independent repair person with the needed skills and tools to fix the board which is that part that hangs off of the display to get yours working again. Otherwise, it’s a new display assembly! MacBook Pro 15" Retina (Late 2016-2017) Display Assembly following this guide MacBook Pro 15" Touch Bar 2017 スクリーンの交換