Hi OP, found this thread via private message from Racer.
This is a brand new issue for me, never heard nor seen anything like it on any display over the years .
I'm going to mirror Racer's current advice by starting with cleartype settings and sharpness settings in your video control panel (the TV doesn't have a sharpness setting in the menu btw).
But while you're at it, in conjunction with your adjusted windows cleartype, try cycling through all of your TV settings again to see if it improves anything.
Let us know how that works and we'll proceed from there.