Open Settings -> Display, if the checkbox "Automatically adjust user interface size in the virtual machine" is checked, the scaling in Win10 VM will be changed into 200% automatically. If you are going to use customized scaling settings, please uncheck it. Then you will never see the popup message that asks for a re-login.
I had unchecked this before the upgrade and it was still off afterwards. Maybe I was not clear enough in my post.
In the same settings, "Full resolution for Mac Retina", can you uncheck that as well.
No, when you turn off "Use full resolution for Retina display" in VMWare Fusion > Virtual Machine > Settings, then you are not able to use the higher resolution for more on-screen real estate (smaller borders, icons, tiles, text etc.) in Windows.
I was specifically talking about the settings in Windows.