I've tested with OC5.7 but it doesn't get any better than this, here's what happens:
I performed the test with the menu apple + suspend activity and also by pressing the on/off button with the same result.
1/ The screen goes off immediately.
2/ After a few seconds, the fan stops then the light on the on/off button becomes flashing.
3/ After about 2 seconds the fan starts again, the light on the on/off button becomes steady again, but the display does not light up immediately.
then the screen lights up for 0.5 seconds and goes off again.
After about 2 minutes the fan stops and the on/off button becomes flashing again, then restarts as before without the display.
Sometimes it happens that it stays in standby with the flashing on/off button without restarting itself, in this case if I press the on/off button it comes out of standby mode, the screen lights up and everything works normally.