Hmm, I am not sure why this is happening, as I have no experience with wing problems. Good luck with your bantam, though, and I hope someone will come along to help you soon.
That looks like split wing. I have a friend whose cochin has the same thing. It’s a genetic abnormality, and isn’t dangerous for their health. However, she could pass it on to her chicks.
I've just been thru this with my new pullets. One girl had this split wing thing when they were all molting into their adult feathers. Was that way for at least a month. I just realized yesterday, it's been resolved somehow for her, she finally shed those few wing feathers on both sides and her wings now look normal. Your girl could have split wing, but if she's a young one, it will probably resolve itself. I kept trying to rearrange the poor girls wings when I was out there, my Indian name should be "annoys her chickens".