I'm guessing it's the new "gaming features" that are expanded on windows 10 lately. I'll post where it's located, but they have added almost like a UI feature set similar to nvidia that overlays everything when you are gaming
"Our title system is an expansion of the titles in the same spirit than the destroyer title. These will NOT be classes and will be completely optional."
Right click lobby.exe and disable fullscreen optimization or roll back the Win 10 updateAlso go into Windows settings, Game - Xbox or Game DVR and disable it.
And big thanks to @Nataz for 3)
No problems here. Playing in (borderless) windowed mode though.