Nothing is wrong. If your default startup state for the PMDG includes PMDG own ground service vehicles, GSX needs to send them away first, before it will call its own vehicles, otherwise you would see them clashing into each other.
Since PMDG has code that runs at every frame that keep their objects attached, making it impossible to remove them as we remove the standard default ground vehicles, we send them away operating the PMDG FMC keypad, and wait for the vehicles to go away.
If you save a PMDG State after the vehicles are gone, you might use it to start your flight always in that situation, so you won't have to wait GSX to send the PMDG vehicles away each time.
