I had a similar issue a while back. My windows 7 vm was not getting updates in the evening due to be in a hibernated state. It was not related to the VM but to Windows. I disabled the Hibernate option in Control Panel\All Control Panel Items\Power Options\ System Settings which did the trick. I also disabled any other sleep settings in Power and Sleep Setting just to make sure. Then I set a GPO to lock the screen after 15min of no activity. Not sure if the issues are the same but figured I would share if it could help.