Force C8 to use one monitor in multi-monitor setup ?

Trying to use DisplayFusion with Cubase 8. Finding some strange behavior with the primary menu bar. It works after starting the system, but after moving the project window to a larger monitor (which is a split on a 4K display) the primary menu bar (still on the primary monitor on the computer) stops working. If I move the primary menu bar to the monitor with the project window it sometimes starts working again and sometimes does not. Anyone having similar problems?