Back since a February beta release, all versions do not go into full screen correctly on my laptop (13" retina 2013 - i5 - intel iris - Sierra).
Screen output remains as desktop - only difference is the mouse pointer disappears and the preview panel is disabled. I can shift the mouse around the screen and when I reach the dock or something the mouse reappears and I can switch applications etc. but when I go back into M8 it still remains in 'full screen' ie no mouse. If I then move up to the menu bar the mouse appears and I can then access the modul8 interface, change controllers etc. however we are still in full screen according to the output menu, and the preview panel is disabled. Comes back to normal when hitting command T.
I always use the syphon output to MM in production, which works fine.
I've mentioned this before in a thread on a specific release, and Pierre asked for screenshots, but I don't think you'll see anything from them.
I'm guessing this is something to do with the os? good luck.