If you just changed runways and added a parking spot without removing the existing ones, it shouldn't affect GSX customization, provided you keep the same name, otherwise you'll entirely lose GSX customization, which in KLAX is fairly complex, since it uses custom pushback routes, custom parking groups, etc.
As I've said, you can check what AFCAD is being used by GSX, by going into the parking customization editor, and read the AFCAD name.
The only update I ran was your new addon manager.
The Addon Manager would probably restored the original AFCAD as it came with the scenery. This means, if you were working on a renamed file, you know have two AFCAD, which means a conflict that will likely cause issues. If, instead, your file had the same name as the one that comes with KLAX, the Addon Manager restored the original one and renamed yours as a .BAK file, making it inactive so, it should have FIXED this issue.