When there is a mixture of windows with different DPIs then specifying a position for a window can end up being incorrectly placed. In the example attached, it will try to place it at -1140 (this may need tweaking depending on the monitor setup) and then check the x value in the title bar. This will end up being something different to -1140.

Another way to reproduce it is to drag the window across the monitors and note that it will jump in the x value when going from one monitor to the other.