1/ As usual developers are never wrong, never make mistakes which explains why there are patches etc...
I don't see how this has anything to do with the problem at hand. Patches clearly show the continuous level of support of a product. Beware of a product with no patches. When we do a patch which was required because of our "MISTAKE", we clearly label it as BUGFIX in the release notes so no, nobody here is trying to hide anything.
However, just because we had bugfix for OTHER issues, doesn't mean THIS is something that we should fix because, obviously, since airport or airplane customization clearly works for most users, if it was really a "GSX bug", it should appear to everybody and, more importantly, you wouldn't have all these users reporting the problem was fixed in some way, without a GSX update.
3/ When I spoke of the catering vehicle of course I thought of its final position before the door.
You mean the approach point ? That's depending on the airport so, the only way for you to affect this, would be changing the airport AFCAD.
The problem I have is I do not know if the starting position of the vehicle whatever it is, is to be considered or not. For instance should I just position the stairs before the correct door without taking into consideration its orientation and position from where it starts on the tarmac?
The starting position has an effect, but only up to a point. You should move a vehicle (one that starts ON the parking, so not the Catering) only if you have a problem or a conflict with an existing object of the scenery but, regardless how you place the vehicle, in most cases GSX *will* be able to figure out a path that will end up with the vehicle correctly oriented to the door.
GSX will fit a curved path that will take into account the starting position/orientation and the door position/orientation, and this takes into account even vehicle minimum radius of curvature, which depends by the distance between its front/real wheels. This means, if you try to make a vehicle to take an "impossible" path, the curve will start to degrade, resulting in strange things like the vehicle doing a 180, because it's trying to reach the door in some way.