Macs used to have a single mouse button as Jobs couldn't see a reason for more buttons and that a <ctl>+click was find. Thankfully Apple discovered how to build decent mice with right-click.
Unfortunately <ctl>+click still remains. Fusion has always had a preference which passes this to Windows. Alas, Fusion 5 has reverted to the bone-headed Apple shortcut by default, so <ctl>click brings up the context menu when attempting to <ctl>drag a file in windows explorer.
You have to change this in Fusion > Preferences > Keyboard & mouse > Mouse shortcuts and click off the Secondary buttion and button 3.
Unfortunately when Fusion's restarted, e.g. after a system reboot, this damn setting reverts.
Can you confirm this is a bug and when it will be fixed.