Not sure if this is SP4 related or windows 10. I used the exact same setup and software (including windows updates) on my sp3 and never experienced this. My setup is onenote (MUI) on my SP4 screen, and everything else on an external extended display. I've only noticed this happen in one circumstance so far. If i have utorrent open, but minimized, if i click on it and bring it up on the external display, onenote minimizes on the surface display. Every single time. Doesn't seem to occur with any other app that i'm currently using. If i take onenote out of full screen drawing then it does not occur. But as i say, this only occurs with utorrent from my experience so far. Hardly the end of the world but annoying none the less. In fact just tried, and even if utorrent is open on the second display, if i click on it, then onenote minimizes. Is there any reason such an event might take place?