Maybe it would have helped to have started training from inside the cage and through the cage bars? Then eventually through the cage door? And after that, work on training in a small room?
Sylphie is a wild caught african ringneck, as per my knowledge. She isn't tame or friendly. I kept her in "small" cages when I first had her, and eventually moved her into a walk in aviary with my cockatiels (introduced at the same time). I later chose to move her back into a smaller cage (and when I saw smaller cage, I mean the HQ Flight Cage) to separate her from the cockatiels. I rolled the flight cage into the aviary, making sure it had a couple of perches inside as well as a water dish. I put the food dish on the outside of the cage in an attempt to get her close to the door. I walked out of the room for a moment, walked back in, and she was inside the cage! Of course, when I walked in, she flew back out!
So, I "booby-trapped" the cage, so when I pulled on a string from the outside, I could shut the door. Set it up and walked out. I remained out for longer this time, but then I started to hear her screaming at one of the cockatiels, so I walked back in. What I saw was her and one of the cockatiels inside the cage. I slowly shut the door with both birds inside, then went into the aviary, opened both doors [to the flight cage] to shoo the cockatiel out, then shut them again and rolled the cage out of the aviary.
She's gotten out three times from the flight cage. Twice, because I didn't have the grate in, and once because a door came open. I never once chased her back into the cage (other than once chasing her off the top of the aviary - she flew back to the top of the flight cage and I left the room - came back in and she was inside the flight cage), clipped her wings, or had to towel her to get her back in. Sylphie would much rather be living in the aviary where she can easily fly around rather than in a flight cage with limited maneuverability, that much is clear. However, right now I'd rather keep her separate.