It's logged as a disk error, there's a recent SMART extended test, if it was before the error run another one, if not keep monitoring, but SMART is showing some issues, so probably going to get more errors in the future.
There's something writing to the array during rebuild, disks 2 and 3 are being rebuilt while there are writes to disks 1, 6, 7, 8 and 9, this will make the rebuild (and writes) extremely slow.
Almost all disks disconnected and reconnected at the same time, including both parity drives which are using a different controller, so most likely a power problem, even if you do anything else for now you should at least reboot.
This has been reported to help:
https://forums.unraid.net/bug-reports/stable-releases/6103-samsung-980-temp-warning-r2007/?do=findComment&comment=20180
Oct 30 02:00:01 thebox kernel: md: recovery thread: check P ...
Oct 30 03:00:01 thebox kernel: mdcmd (63): nocheck pause
This suggests parity is set to pause after 1H, try re-applying the scheduled parity check settings.
Unassign one of the data drives, start the array, if the emulated disk mounts and contents look correct rebuild on top, once the rebuild is complete repeat for the other data disk.