I just got a Magic Mouse that I'm using with MacBook Pro (15", 2015), macOS Sierra. I've noticed a problem where, if I'm in a window that has multiple areas with scrolling, if I start scrolling in one area, lift up my finger so I'm no longer scrolling but the inertia is still going, and then move my mouse over another area, the scrolling inertia in the first area will stop, and will continue in the new area. I've found this in multiple apps (Discord and Chrome so far), and in the case of Chrome, multiple web pages. One example is Facebook - if I hover over the news feed, make one quick swipe down the mouse so that it starts scrolling, then quickly move my mouse over the chat window, the inertia from that movement will stop in the news feed, but the chat window will scroll down.
This doesn't happen with my trackpad, only with the Magic Mouse. Has anyone else encountered this before? Any idea what to do about it? I know there's a way to disable inertia scrolling via Terminal, but in general I like inertia scrolling, so that would be a last-ditch solution for me.