Thanks for writing in, welcome to the community. Sorry to hear that you're having some issues with the voice prompts of your SoundSport Free's. We appreciate you taking the time to already look into some troubleshooting.
There is not a factory reset available for these. But there is some further troubleshooting we can attempt.
What happens if you turn off the voice prompts of your headphones? If you go into the Bose Connect app, and visit your product settings you can toggle this feature on and off.