Disk Not Ejected Properly macOS Sierra
I upgraded to MacOS Sierra a couple of days ago and ever since, whenever my MacBook Pro (Mid 2015) goes to sleep my external hard drives (all but Time Machine) are disconnected. Upon waking the computer I get the "Disk Not Ejected Properly" alert. I was not having this issue prior to updating to the new OS. I've tried restarting the computer and experienced the issue again. Please help!
All of the drives are running through a hub - which has never given me issues until the Sierra update. The two drives disconnecting are portable drives (1 Western Digital, 1 Seagate). My time machine (which isn't disconnecting, also a Seagate) is a powered, desktop drive.
Any help would be appreciated. Thanks!
MacBook Pro with Retina display, macOS Sierra (10.12)