Partly why throttling helps is because when you use a server-side redirect (res.redirect()), the browser immediately stops processing the current request and starts a new one for the redirected URL. This behavior can lead to pending asset requests (like images) being canceled or not fully processed, especially if the redirect happens too quickly.

If you need to retain 302 redirect, I'd rather move the redirect to the front-end side and work with the browser directly there, allowing it to wait for assets better than in the case of server-side redirect here.

Call your POST endpoint receive response and redirect from the client-side. Let me know if that solves the issue