For some months I had to press a spot on the lcd driver board to get the right third of the screen to stay on.
Eventually I got tired of that and shelled out $150AU for a replacement panel.
Now nine out of ten times it boots up like this.
I guess it's an EDID issue but can't find a way to fix it.
Fortunately it Wakes from sleep ok so it's only a hassle when I have to reboot.