The problem is caused by the simulator itself automatically closing the door at the same time when GSX is also closing it, resulting in a reopening because the command is sent in the middle of the door animation.
This happened because we moved the door closure during departure earlier, because in previous version the closure of all doors during departure happened after the Tow truck connected, and several users asked to close the doors earlier so you won't see a door open for all the time it took after the jetway retracted until the tow truck connected, which of course was a correct suggestion.
However, this conflicts somehow with MSFS automatically closing the main door (only) when a jetway retracts, which is something we never noticed before ( has been added in a recent update, maybe ? ), so in the next update, to be out Tuesday together with SU12, if a parking has a jetway, the doors won't be closed so early, since it's already taken care by the sim, but of course they'll be checked (and eventually closed ) again when the Tug connects, because the other doors won't be closed automatically by the sim, only the main exit.