Well there is no Code-Logic involved in that Case, it is manual Selection (until arriving at the Gate). Basically the In-Game Menu is replaced by the StreamDeck - where I browsed the Gates, selected A15 and answered "no" to the Follow-Me. I just hadn't answered the Operator there.
The Code-Logic that takes over at arriving at the Gate (Engines Stopped -> Call Jetway/Stairs. Beacon Off -> Place Plane-GPU/Chocks, Start Deboarding) does take Operator Selection into Account. But I have to admit, the Code is expecting it to happen after the Jetway (or the Stairs in case of a Parking Position) is selected (Menu -> 5/6 -> Check Operator Selection).
Did not find a way to reproduce it after it happened - whether via In-Game Menu nor via StreamDeck Menu. So I couldn't share a more detailed Description :/
Using GSX completely without the In-Game Menu works normally very well and without Issues even on Sessions with Turn-Around.
I surely can share you the Code if you want to check it! But that was not the Intention - I just wanted to share a Crash of Couatl which is just something that does not happen for me during normal Operations