It seems like a problem of the airport elevation in the scenery AFCAD not matching the actual elevation of the airport, probably because they don't have a better way of solving the problem of ground flickering when doing the scenery ground as a 3d model over a platform, which is what we also use for our own airports, but without inserting the wrong elevation value in the AFCAD, because we have other methods to solve ground flickering.
There was a similar issue with Madeira, which had the altitude in the AFCAD set 9 meters *below* the real one, just that with this one, they made the altitude difference a bit less, so it's not enough to give the impression that GSX vehicles "disappeared" because of some kind of GSX problem, but enough to sink their wheels.
We think the elevation in AFCAD file should be always as correct as possible, because it won't affect "just" GSX, but potentially any other addon that needs to read the AFCAD for any reason, and there are other ways to prevent ground flickering of native 3d FSX scenery over a platform without having to resort to such tricks ( KDFW, CYVR, JFK V2, and all our airports that have 3d taxiways have their ground made as 3d model over a platform, but the elevation in the AFCAD is the correct published one ).
But in any case, GSX being the flexible program that it is, can be easily updated to add an "Elevation override" in the airport customization, so it will be possible to tell GSX to ignore the AFCAD elevation and use a different one, and that will be available as an FSDT-provided airport customization (at least for these two Aerosoft airports that are well known to have this issue), AND as an user customization option in the scenery .INI file, so new airports that will eventually released in the future that will still use this method, can be added even without our support.
In fact, it's one of the things we were already working on, and will likely appear in the next major upgrade, which is currently in Public Beta.
