Background
I have Xenial Xerus installed on a Mid-2014 Macbook Pro OSX High Sierra host, running in a VMWare Fusion 10 instance.
On Fusion 7, I had no issues with Ubuntu on VMWare. However, since I also virtualize my Bootcamp partition for convenience... I was forced to update to 10 since 7 no longer supports loading Bootcamp on the latest OSX.
VM specs
3 Cores, 4GB ram, 20GB HDD (10GB free), Hardware version 14. 768MB VRam
Issue
I just cannot ever restart or shut down the VM. If I restart or shut down Ubuntu, on the next reboot, I get the message: "Sata device 0:1 could not be connected, always try to connect when starting this VM?". Then, Ubuntu starts in low graphics mode, and I am forced to restore a snapshot of my VM when it was working. This is workable, with proper snapshotting and backing up I have been passably using Ubuntu. However, I have had to go into the console in low graphics mode after a crash and back up my work, restore snapshot, and restore my work many, many times. Conceivably if I ever start leaking memory and need to reboot, I'll need to re-image the VM again.
What I've Tried
Different allocations of ram, cores.
Reinstalling x-desktop
Reinstalling/updating Nvidia drivers (this broke the hell out of the VM when I tried)
Reinstalling VMWare tools
Reinstalling Ubuntu.
Installing all manner of different desktop environments
The low graphics mode in VMWare issue was resolved by doing a apt-get update and upgrade. Turns out, the 16.04 LTS on Ubuntu's repository does not contain drivers that are compatible with VMWare on Mac. VMWare 10 (though it is not stated anywhere in documentation or otherwise) requires updated system applications and drivers not provided in the vanilla distribution.
I have no idea why the VM only broke after a reboot, but such is technology.
For safe measure, I also increased my graphics memory allocation to 1024MB (up from the recommended 768MB)