Thanks for the quick reply @Falkentyne, flashed back to 1304 to check again, and resume from sleep/S3 *does* seem to work okay (at least a couple of times). It's resume from hibernate/S4, specifically, that is the problem.
0x97 Q-Code is officially "Console output devices connect". There seems to be some received wisdom that it's graphics card related but unsure if that is confirmed - or whether there are other components under that code. "Output devices" potentially includes a range of items.
After it hangs on initial recovery from S4, it *will* resume correctly after a stab of the reset button. So it's not a major problem but it's a completely consistent one. And a pest at the moment as I'm routinely using S4 due to a peripheral that (hopefully temporarily) doesn't like resuming from S3.
I've checked what it does when the hybrid aspect of hybrid sleep is leveraged too (i.e. it more or less becomes a resume from S4). Put system to sleep, turn mains off, wait, turn on, power button... and it resumes correctly.
So there is something specifically wrong with the way it's resuming from a hibernate cycle that is odd.
The lack of verbosity in Asus' release notes doesn't help working out what might be causing it.
