I have experienced a very similar failure, although on a much smaller monitor; turned out to be a dirty/loose connector plugged in to the side of the LCD panel internally. Free broken screen to working score in less than an hour.
Suggest popping it open and checking for just such mischief, and scanning for cracked solders at the same time; main focus the area most responsive to the hits, bet you find something loose there.
If you smoke/have pets/live in a dusty environment etc. such failures are more easily manifest.
Disclaimer: Don't do it if you can't without having a shocking experience, goes without saying that the plug should be out overnight to let the aforementioned caps discharge via paths that do not include your a**.
Although these days they are weaksauce, the old tube sets would, yes, really put you on your backside.
Proceed with caution. And rubber shoes.