This issue is rock solid easy to reproduce. I've been running this rack server for almost a year now with no issues on 14.04. Ended up with a corrupted OS disk so decided it was time to upgrade to 16.04. All seemed well for a few weeks until it came time to run backups on my workstations and copy large (10+ GB) batches of files. Every time like clockwork, it will get to around 20-30% complete on the copy job (from Windows workstations) and then the server drops off the network. Samba share becomes inaccessible and I cannot ssh into the box. Upon firing up the server's monitor (or looking at syslog) I see when the issue occurs the server throws two (or more) general protection faults. Initially taking a stab in the dark I decided the only thing I did different this time around was configure my two NICs into a bonded interface. I removed the bond and went back to the onboard NIC only and it still does it.
Pastebin link is syslog of all the faults when they occurred last night after I reconfigured the NICs. http://pastebin.com/NnjMreie
Server setup is 16GB of RAM, 6 1TB drives in raidz2 (RAID6), 2 4TB drives in zfs RAID1, and 2 500GB drives in a md RAID1 array for the OS. If you need more information I can provide it.