Whenever you have positions wrong in GSX, it's always a problem of what AFCAD is being used by GSX.
You can first check which AFCAD is being used by GSX, with the "Customize parking positions" menu, the page that will open will indicate the name of the AFCAD in use.
It's not the one that comes with the scenery, there might be several reasons for this:
- There's another AFCAD for the same airport on an higher layer in the Scenery Library so, you must either remove it, or put your airport on an higher layer, then restart FSX to apply the changes.
- The AFCAD included with the airport has some kind of error, so GSX discarded it.
- For some reason, GSX didn't detected you installed the scenery, so its scenery cache is outdated, in this case, try to force a cache rebuild, by removing the following folders:
C:\ProgramData\Microsoft\FSX\SceneryIndexes
C:\ProgramData\Virtuali\Couatl
And restart FSX, you should see both FSX and GSX rebuilding their scenery caches, the new scenery should work at the end of the process.