Tiny bug with DF's notification icon context menu. If the context menu opens too close to the left of my screen, it actually pops up on the adjacent monitor.
As you can see, I've got my taskbar separating both desktops. (That's monitor 2 on the left.) By right-clicking too close to the left edge of the right monitor, it causes the menu to appear on the other montior. I prevent this by sticking the icon in the flyout box, which makes it appear far enough from the edge to keep the context menu in the right spot.
I know about this, and it's a silly .NET error. I'm not sure I can do much about this without creating my own custom menu, or overriding many of the default behaviours of the standard one. For now I'm going to leave it as-is, as I don't have enough time to re-write everything I would like.