Redirect URL being treated as relative to user page

Normally when you expect an "internal path" you don't need to start with a /. For example, to redirect to node 1 I would use a url of "node/1". However, when I do this it tries to redirect me to /user/node/1.

You might want to do something like this:

$url_object = \Drupal::service('path.validator')->getUrlIfValid($path);
$url_object->setAbsolute();
$url = $url_object->toString();

to validate and get the correct internal path.

Also, when doing the redirect, you should probably use a status of 302, like:

$response = new RedirectResponse($url, 302);