The only possible reason for any problems with a custom operator you made with the PaintKit, is that you made some errors in one of the files but, of course, it's not possible to say without looking at them.
The name of the operator is taken from the couatl.atc_parking_codes lines so, if you use a custom operator, the line must indicate it's plain name, and nothing else because, if you use codes, they might match another operator that might be included in an internal list of GSX operators.
So, in your case, be sure all the couatl.atc_parking_codes lines in ALL vehicles in your custom set will read like this:
couatl.atc_parking_codes=Flightway