Are you using any 3rd-party kernel extensions? If so one of them could be crashing the OS. The procedure in this article will list them:
http://osxdaily.com/2010/08/03/list-all-third-party-kernel-extensions/
How are you copying that amount of data? Finder? Have you tried copying the data using a Terminal command or via a copy utility? In general I wouldn't trust Finder 100% for copying hundreds of terabytes. It also has no "on error, resume" capability.
Are all these drives HFS+ (except for the NAS)? Are any of them exFAT or NTFS using the Paragon driver? That is a kernel extension that could theoretically crash the OS.
Are any of your RAID arrays managed by SoftRAID? That is also a kernel extension. In my experience both Paragon NTFS and SoftRAID have been reliable but an OS panic calls into question all 3rd party kernel extensions.
Before you copy hundreds of terabytes, it's a good idea to run Disk Utility First Aid on both source and destination disks. I would also run it afterward on the destination.
Copying files via Terminal:
http://osxdaily.com/2010/08/03/list-all-third-party-kernel-extensions/
After copying that much data you ideally should validate it all got copied. I use Beyond Compare for this. There is a Mac version:
https://www.scootersoftware.com/index.php
You can also use the 3rd party tool IntegrityChecker to create a CRC checksum and then verify that after the copy:
https://diglloydtools.com
There are various other 3rd part copy utilities but I haven't tried these, just listing them. Before you use any copy utility or Terminal command full scale, it should be tested on a small data set and the files checked.
CopyCatX:
https://www.subrosasoft.com/product/copycat-x/
UltraCopier:
http://ultracopier.first-world.info
RapidCopy:
https://itunes.apple.com/us/app/rapidcopy/id975974524?mt=12
Hedge (designed for camera offload but useful for reliably copying files):
https://hedge.video