Buggy when used with Spaces

As reported by Joe F / Mergesort

• “There seems to be a bug where I wouldn't be allowed to ⌘Tab to apps on another space when Substage was active, it would just shoot me back to the space I was on. My exact configuration is: 4 spaces, 2 full screen apps, and Finder is set active to all spaces.”

• Substage window not moving between finder windows (sometimes? when spaces active?)