I've been noticing that the browser preview doesn't always update to the page that is currently open in BSS if you've changed pages with the browser preview not being focused. In other words, I'm utilizing that nice new feature (TY FOR THAT TOO!!) so that I can update without it lagging with each update. I'm utilizing this by just changing to another tab in my browser so that updates don't get reflected in the browser preview until I switch back to that browser tab. But ... as I said above. If I change pages while the browser preview is not the focused tab in my browser, it doesn't always update to the page I have open in BSS, it will update, but it only updates whatever page I had opened at the time I changed to a different browser tab.
This isn't 100% of the time, and I haven't tracked down what times it does and what times it doesn't, but it almost always does it when it's been defocused in the browser for a while. So far it's almost all the time for me though that it doesn't change the page.
Page changes fine if I switch when the browser preview tab is in focus so it hasn't broke anything in that way, just when not focussed.
Let me know if you need more info.
Mac Version - El Capitan (not brave enough to upgrade yet haha).