That could be, if the window is outside of the available space, for example the height is somewhere between 1280 and 1920, while you are on the larger display, then open it after youve moved to the smaller display, it might just default at that point since it literally cant display it at the previous res. What happens if you go the other way? Smaller res to larger?
The change in res may make it default period, regardless of window size too. Who knows.