Right? Super weird. The ROM has been danged near perfect otherwise.
I don't even know where OmniSwitch or Slim recents are, I tried to find them in the settings menus after it starting doing this. Where would I find it?
No playing with Xposed stuff either. My wife was reading an e-book on it last night and it was working as far as I could tell. I went to put it away and the square button didn't do anything. It registers that I pressed it (screen reacts with proper animation), but it doesn't bring up the recent menu. I did a reset, still didn't do anything. That's when I tried clearing cache. Where do I find the OmniSwitch and other stuff?
Go to Settings, click on "search" icon - type "recents" or something like that, choose "use OmniSwitch as default", open OmniSwitch application and enable it (you can disable green color in "Configure drag handle" using a slide to make a transparent color). Then see what happens when you click on recents button.
And by the way, I use OmniSwitch as default, it has "favorites" feature and it's simply the best tool for recents in my opinion. Good luck.