OSX outputs are overlapping
This happens when you had previously assigned Resolume to use a specific Virtual Desktop. This means it will try put all its pixels on it. It's ridiculously easy to activate this option by accident. Annoyingly, OSX won't let you change it back unless you have more than one Virtual Desktop.
So, first open Mission Control. The default hotkey is CTRL + up arrow. On a laptop, you can also use three finger swipe up on the trackpad. Mission Control is also activated when you drag an application window to the top of your screen. You can also find Mission Control via Quicklook or just look in Applications.
Once Mission Control is open, a grey bar will appear in the top of your screen, showing you all your Virtual Desktops.
Move your mouse to the far right of the bar and a plus button will appear. Hit that bad boy. Congrats, you now have a second Virtual Desktop.
Now go to Resolume's icon in the Dock and right click it. Because there are multiple Virtual Desktops, you can now choose where to assign Resolume under Options.
Choose Options > Assign To > All Desktops. Boom. Resolume will understand you want to use all desktops again and your output will work as expected.
If you like, you can go back to Mission Control and delete the second Virtual Desktop you just created. Because you have Resolume assigned to use all Desktops when you deleted it, things will continue to work as expected.
PS this problem also appeared on Windows in early versions of Resolume 6.x. It looks identical, but it's a different problem with a different solution. It's fixed by updating Resolume to the latest version.