Выполнил
# vboxmanage controlvm Win2016 savestate  
0%...10%...20%...30%...40%...50%...60%...70%...80%...90%...

Минут 20 оно в таком состоянии висит, и не помогают ни
# vboxmanage controlvm Win2016 poweroff
VBoxManage: error: Cannot power down at this point during a save state
VBoxManage: error: Details: code VBOX_E_INVALID_VM_STATE (0x80bb0002), component ConsoleWrap, interface IConsole, callee nsISupports
VBoxManage: error: Context: "PowerDown(progress.asOutParam())" at line 231 of file VBoxManageControlVM.cpp

ни
# vboxheadless --startvm Win2016
Oracle VM VirtualBox Headless Interface 5.1.38_Ubuntu
(C) 2008-2018 Oracle Corporation
All rights reserved.
VBoxHeadless: error: The machine 'Win2016' is already locked for a session (or being unlocked)
VBoxHeadless: error: Details: code VBOX_E_INVALID_OBJECT_STATE (0x80bb0007), component MachineWrap, interface IMachine, callee nsISupports
VBoxHeadless: error: Context: "LockMachine(session, LockType_VM)" at line 946 of file VBoxHeadless.cpp

при этом пишет, что запущенных виртуалок нет
# vboxmanage list runningvms
пусто

В логе
7:33:24.315307 SSM: Successfully saved the VM state to '/root/VirtualBox VMs/Win2016/Snapshots/2018-12-04T12-07-27-528650000Z.sav'    
27:33:24.315313 Changing the VM state from 'SAVING' to 'SUSPENDED'

Можно ее как-то оживить? Может сервер ребутнуть?