i nearly had the same problem today, after reboot no hard drives found
tried to shut down the dns through browser without success even though browser said the dns is shut down.
took a closer look, power led was off....the two ledīs for disk were still on, fan was not spinning
i didnīt want to risk anything by pressing the reset button as the dns would reboot with my disks still inside so i pulled the power plug, took out the drives, waited 10 minutes, reinstalled firmware 1.03, this time shut down worked, placed the drives back and loaded my settings backup......now itīs working again.......at the moment
if a newer better firmware doesnīt come soon iīll replace the nas with a better brand.....restoring over 5 tb justs takes too long