What is EDID and how does it affect WATCHOUT?
EDID - Extended Display Identification Data
To use a simplified explanation, EDID is the handshake between the display computer and the projector/screen – making sure the content is displayed in a certain order when using multiple outputs.
If you have a display device connected at startup, and then you remove it, and after that plug it back in you need to re-start WATCHOUT since WINDOWS will have re-arranged the desktop which makes WATCHOUT loose its references.
The best way to avoid this kind of situation is either to add some form of EDID emulator box (or device) on the display output of the display computer, or use a display server with a graphics card with built in EDID management.
If you make sure that the EDID emulator never looses power you will not see any problem of this kind. This helps especially if you use consumer graded displays/projectors since they almost always drops the EDID when powered down, to comply with the power savings regulations.