Well of course nothing software related will help, it's a hardware issue. You've got what I like to call. 'The ribbon-wear of DEAT*FIZZLE* AAAAH' (with a couple of cartoon sounds involved of course)
AAAANYhow. What you're seeing right there is the ribbon's not sittin' right. You checked the hardware? Exactly how? Did you open up the laptop case itself and check the internals of how the cable's sitting?
Here's the surprise. It's NOT the seat! It's ACTUALLY usually the cable itself. There's an internal fray or damage, or even quite possibly, the terminals on the screen ITSELF inside the lid is not connected properly, and let me tell you, it's a REAL mess getting to that part of the laptop, believe me, I've been there.
The reason why it's getting worse is because the heat generated in the wire is SHIFTING the cables / components around eeeeeeeever so slightly, changing the contact and thus, eventually going FIZZLE! Rainbow everywhere.
You've got three options.
1: RMA the machine.
2: Buy a whole new screen panel with included ribbon and fit it in yourself.
3: Live with it and achieve the inner Zen Master to journey the quest of finding the 'Sweet spot tilt'.
There's the VEEEERY odd chance that it's actually the terminal on the motherboard, however, your slight screen tilt confirms in my suspicion that it's the ribbon itself.
....... a side note, it's not even a ribbon, it's literally a long 6 inch black cable. ;d