Text generation within AI models is a known limitation, and Firefly is no exception. Adding text or symbols directly during the generation step can sometimes be unreliable, even when quoted.
One good option is to generate the image without the text/symbol and then add it afterward in Adobe Express.
Another workaround to fix distorted text in previously generated outputs is to use Boards. Load your generated image with the misspelled text, choose the three dots (...) option, then Edit text in image, and you’ll be able to correct the spelling.
Fix text in Boards
I hope these steps help you achieve the result you’re looking for. Please let us know how it goes.