That message you see it's coming from SODE. It's not possible to say more, if you don't indicate precisely:
- the scenery used. If it's not default or an FSDT scenery, indicate the scenery precisely.
- the gate used.
- if you made a customization for it. If you have, supply with your .INI file.
every single gate/jetway and parking position is tested and customized for the largest possible aircraft from the fleet I have that can fit in the spot
Testing with the largest airplane will not guarantee it will always work with everything. I would rather test with a medium airplane instead, something in between the smallest and the largest plane that can normally used on that parking.
But again, fact it worked on a 2nd try, seems strange. Note that, from the moment you accept the selection to dock a jetway in GSX, what happens next is handled by SODE, GSX sends the airplane doors coordinates to SODE and a "dock" command so, unless the airplane configuration changed ( or the airplane moved ) between each try, from GSX side, the data sent to SODE is always the same.
If it happens again, provide with the SODE log, which can be checked in the SODE Platform Manager.