Hi, are you facing this problem on every flight/every time you load in?
Please also try to empty the contents of this folder (delete the files inside, not the folder itself) and relaunch the sim.
Steam version: %APPDATA%\Microsoft Flight Simulator\Packages\inibuilds-aircraft-a300-600
MS Store version: %LOCALAPPDATA%\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalState\Packages\inibuilds-aircraft-a300-600
This will reset all the generated files & config of the A300 to default. Just to ensure there wasn't some issue on the initial load where it didn't compile properly.
Thanks!