Hi there!
I recently bought the A350 for MSFS 2020. Most of the times when I spawn into an airport(custom scenery and default), the plane spawns at a random position, sometimes in the airport buildings or in the grass. I also use GSX if this might help solving this problem. I will provide example Pictures.
1) The first one shows the spawned plane.
2) The second one shows gate F33/35 at Vienna, where i selected to spawn the plane.
3) The thrid one shows where it actually spawend(the custom position/benutzerdefiniert)
https://imgur.com/a/6dKNRPg
Best regards