As explained in so many threads in the forum, whenever you have missing *parts* of objects, the problem is never GSX, but it's always something wrong in your graphic settings, usually a setting or an undocumented tweak which is not right for your card. Try all of these:
- Reset your video driver to default
- If that doesn't work, try to delete your FSX.CFG, so a new one will be created with all default settings. Apply only the HIGHMEMFIX = 1 tweak and nothing else, if you use FSX. If you do this, you must reinstall GSX, because the installer needs to add the Addon Manager folder to the list of Simobjects, and they will disappear if you just reset the FSX.CFG to default without reinstalling.
- If that doesn't work, be sure you are not running the sim or any of the addons that starts with it in Compatibility mode.