Sometimes these models get tripped up with a mistake. They'll add a comment to the code saying "this is now changed to [whatever]" but it hasn't made the replacement. I tell it it hasn't made the fix, it apologises and does it again. Subsequent responses lead to more profuse apologies with assertions it's definitely fixed it this time when it hasn't.
I've seen this occasionally with older Claude models, but Gemini did this to me very recently. Pretty annoying.