The RC9200 uses older passive matrix screen technology, which is susceptible to this sort of thing. For example, if you put a black box in the middle of a white screen, the box will "smear" vertically and horizontally. This is due to how pixels are addressed in that type of screen. It isn't an issue on active matrix screens (which is used in EVERYTHING these days, as well as color Prontos from the NG series forward).

The effect can be reduced by keeping high contrast areas to a minimum, and avoiding lining up such areas (which doesn't really work in remote applications).