/music/rand and the other song endpoints return a different song from the same URL, but the responses had a Last-Modified header and no Cache-Control, so browsers cached them. The same song played again and the server never picked a new one, so /music/addQue added nothing. Send Cache-Control: no-store again, as the server did before the rewrite. Also allow the Cache-Control request header in CORS, which the frontend sends to bypass responses that browsers have already cached.