I have a 2015 13" MacBook Pro that is up to date with Sierra. For at least a year now I will occasionally get a "dead zone" or unclickable area that doesn't respond to any mouse actions. It is close to the middle of the screen but not exactly. Which ever app is active will not respond to and mouse clicks or scrolling in that area. If I move the app slightly I can then click in that area. It happens with all applications. It will resolve itself after a reboot and eventually come back. It seems to only occur when using an external monitor but that might just be because I use one 90% of the time. I am guessing some weird software thing is happening where it thinks there is a window in that area and button clicks are being sent to something else. Anyone ever see something like this before and fix it?