Nobody ever reported this before. Are you sure these stairs are all coming from GSX ?
Or, it's possible you have edit the default 737-800 configuration, either the GSX one or the FSX aircraft.cfg ? It's not very clear from your message, if the problem happens ONLY with the default 737-800, or with other airplanes too.
To rest the GSX config for an airplane (in case you have edited it and are suspecting made an error), and revert to the one that comes with GSX, go into the Aircraft configuration menu under the "Couatl powered products" menu, and press the Reset button, allowing to go back to the standard GSX config.