How to replace double quotes within a string (only in the middle)

I asked this question to chatGpt, he gave me this regex and example:

let str = '"This is a "test" string with "quotes" in the middle."';
let result = str.replace(/(?<=^|[^"])(")(?=S.*")/g, 'replacement');
console.log(result);

But I still get the first double quotes in the begining of the string replaced

//replacementThis is a replacementtest" string with replacementquotes" in the middle."

I need only the doubles quotes in the middle to be replaced, not in the beginning or the end.