ReadyNAS 1000S - Firmware & 3TB HDD Support?

Okay, so here's where I am now - after re-reading the documentation and searching the forums, I found that the RAID type has to be selected prior to reloading the factory settings, so I am now up on a functioning RAID5 array. However, in the interest of having all of my customer's files ready by Monday morning, I've interrupted the RAID resync (I think this is the correct term) by pulling the 4th drive so as to have better write speeds while I work to move over 300GB of data back to the NAS. I've been trying to restore files from a backup for some time now but am running into situations where the NAS is rebooting itself and cutting off my file transfer. There are no helpful messages in the log - just a generic message about the NAS coming back online after an unsafe shutdown.

Could this be because the array is degraded? I'm using Microsoft's SyncToy to copy data from my backup USB hard disk that's connected to my workstation, over the network, to the NAS share. I'm seeing write speeds of ~70megabits on large files so I can't imagine that I'm thrashing the array to the point where the NAS is rebooting itself. I'm primarily working with small files, lots of Word documents and PDFs, probably close to 300k of them that need to be copied.

Should I rebuild the RAID5 before trying again or could something else be wrong? My "Monday morning" deadline is less than 5 hours away and with 200k+ small files, I'm certain that I won't be able to keep this promise.

Edit:
After scrolling through half a dozen pages of forum search results, recalibrating the fans was suggested. I thought this was silly (temperature sensors were fine and RPMs were consistent) but tried it anyway - no random reboots so far.