The problem is caused by two issues:
- The very close proximity of the Sedes Airbase ( LGSD ), which is lower than the default range (3NM) that GSX checks to guess which airport you are located so, depending on where you are located, GSX might have switched to the other AFCAD, because its ARP was closer to your location.
- An unusual way to create an elevated taxiway, by using a separate AFCAD with its own fictional code ( ZGTS ) that contains only a ground polygon (and I guess setting the altitude too)
Both issues can be fixed using the
airport_visibility command, explained on the GSX manual at page 21, and also discussed here:
http://www.fsdreamteam.com/forum/index.php/topic,11770.msg90088.html#msg90088and here:
http://www.fsdreamteam.com/forum/index.php/topic,12126.msg92297.html#msg92297Since the LGSD Airbase doesn't have any parkings, so it's not usable by GSX anyway, it would best to just disable both of them, adding the following lines to the [GSX] section of the %APPDATA%\VIRTUALI\CouatlAddons.ini file:
airport_visibility_LGSD = 0
airport_visibility_ZGTS = 0