I created a new app and added a couple tables to it. I'm stuck in the sandbox editor though. When I click save or publish it flashes the grey bar "still working on it" and it goes away really quickly.
When I try to play the app, or switch to classic view or anything that would take me to another screen, I get the unsaved changes prompt. Clicking Save and continue here does the same thing. Really quickly you can see the "still working on it" grey notification and then it goes away.
I've tried another computer, another browser.