Browser popups on wrong screen
Since upgrading to Sierra (I don't remember this being an issue before) and when a second monitor is connected, all browser popups are now loading on the main screen and not the screen that the browser is located in. I have a pretty large ultrawide screen as my second screen so it's a bit of a hassle to mouse over to the other screen to accept or acknowledge the popup. I mostly use Chrome but this happens in all browsers.
MacBook Pro, macOS Sierra (10.12.2), Crome Version 55.0.2883.95 (64-bit)