Well, as a customer I'm a little disappointed by your response, to be honest. And I don't quite understand all of it.
I highlighted the main issue here.
If the wrong number of passengers were sent, how come that in the final number of passengers is totally correct??? It's just the first bus that is wrong, not the number of passengers.
Because the number of passenger is checked again before the first passenger is created. As I've said, the issue is because it was set too late by the airplane, after GSX already decided which Bus to create.
Saying GSX is NOT sending the wrong bus is just plain wrong. It is your product that is not working correctly in this situation. It's a GSX bus-model with GSX passenger-models. How is this "not GSX"?
Wrong. To you GSX is not working correctly, but only because it's not getting the data it needs to work correctly from another addon.
If it would send the wrong number of passengers to trigger a mini-van, why are over 30 people exiting the van and not just the (wrong) number of 6 or so?
Already explained above.
Why does it work when I do everything the same way and just skip (re)fueling?
Because the type of vehicles that will be used, it's decided by GSX only once, when the first service is called. This is because to search through all available vehicles takes some time, so GSX does it only once, not each time you start a different service in the same parking for the same aircraft, since all the conditions that would affect the choice of vehicles would be the same. Of course, as long as GSX is used stand-alone, this won't be a problem but, if it must depend on external data supplied by another add-on, this must be taken into account.
We already had another chat with FS Labs devs, and explained about this so, it should be enough for them to set the control variable with a reasonably high number of passengers that won't result in the minivan or the shuttle being called ( any number higher or equal than 18 will do, since the Bus will be used starting from that ) as soon as the airplane starts, so even if the GSX session starts with the refueling, the Bus will always pre-selected and, considering GSX re-check the number of passengers again before generating them, the final/correct number will always be shown.