Due to the way GSX detects scenery changes, it cannot detect a file rename or removal, otherwise it would have to scan each and every file at each start, making it very slow but, instead, it only checks the folder last modification date, and this doesn't change after a rename/removed from a folder, which means, if a scenery file has been renamed/removed, you MUST select the "Restart and rebuild the airport cache" option from the Couatl menu after the renaming took place.