If you enable drive encryption it will cause your file transfer speeds to drop from 80 mbs to 12mbs, quadrupling the time to a crawl and lock up the CPU at 100%. USB to NAS with an encrypted drive will lock up your CPU and cause the drive to stop working
I have replaced cables and routers and return two unit. Search the boards and found no answer.
Hopefully this will help because it was a hassle.
If you are using JBOD, you can encrypt one drive and leave the other drive as decrypted when formating.
I ran this benchmark and only got 13 MB/s with encryption on and than turned it off and the CPU does not lock up at 100 percent.