This is STILL an issue in Windows 10 with Dual monitors and it seems to ONLY affect the default monitor. When the window is maximized or snapped to the top of the screen, the title bar and the File menu disappears and seems to be transparent to clicks through
to the desktop. If you click in that "blank" area you are actually selecting the desktop so the current window is no longer active.
What I've found is you can take the window out of maximized mode by clicking in the window to make it active, then hit the Alt-Spacebar to select the Window Control menu, then click "restore" to take the window out of maximized mode.
I've also found that if you turn off the Auto Snap feature in the Multitasking settings, the window won't snap to the top when you drag it close to the top. This helps because the window doesn't then auto maximize.
I have not tested it with Auto Snap turned off and then click the maximize icon in the upper right. But I know with Auto Snap turned on and clicking the maximize icon, the issue occurs.
Any response regarding this issue aside from reinstalling windows, the display driver, anything... from #Microsoft would be appreciated. We shouldn't have to reinstall anything.