Not a GSX bug, not something we can fix, and it's depending on the camera view settings. The simulator clips automatically polygons depending on the Near/Far clip settings of the camera you use, which can change further if you use non-default camera utilities.
There's a limited precision in the zbuffer, which makes impossible to create a camera view that will work equally well in the distance ( not showing flickering ) and from very close ( not cutting close planes ), it's sort of a compromise we don't have any control over.
