I am inclined to think this is a Windows API bug (What?! Windows has bugs? )
Anyhow, I noticed that non-resizeable dialog boxes (Like a regular Msgbox) are not getting placed correctly via WinMove.
Below is a screenshot showing Msgbox overlapping my other monitor. The window is at the right x coordinate (in this case, left monitor x is 1366, and the Msgbox x is 1366), but, as you can see, it clearly it being placed incorrectly.
Has anyone else noticed this?