I have multiple monitors.
Using
Let>MSG_XPOS=100
Let>MSG_YPOS=100
Message>Hello world
Works fine. The message window appears in the top left of my first monitor, at X=100, Y=100.
However, if I use MessageModal instead;
Let>MSG_XPOS=100
Let>MSG_YPOS=100
MessageModal>Hello world
The dialog appears on my second monitor, at approx 1252,100.
If I set XPOS to be -1000, messagemodal's appears on my first monitor (but then Message dialogs appear off-screen).
Edit: This also appears to happen with "Ask" and "Dialog" windows too.