Is there a way to fix an image in Firefly, or are we subject to whatever the AI generated?

You can try write explanation prompt about the arms. but the alternative is to do how @DeanUtian said.

You can use Generative Fill to replace part of the image with something new.
Here's info on teh tool in Photoshop. You can use it in Firefly site as well:
https://www.adobe.com/products/photoshop/generative-fill.html  

First of all I would download it as is.

Then you could try two things: generate another fairy, hope for a better arm and then use Photoshop to bring a perfect arm into the other image.

Or try and use the Replace background module.

in the future, to find the best place to post your message, use the list here, https://community.adobe.com/

p.s. i don't think the adobe website, and forums in particular, are easy to navigate, so don't spend a lot of time searching that forum list. do your best and we'll move the post (like this one has already been moved) if it helps you get responses.

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