RedirectToAction throwing 503.2 "Bad Gateway Error"

503.2 Error

[HttpPost]
[Route("Account/LogIn")]
public async Task<IActionResult> LogIn(SignInViewModel model, string returnUrl = null)
{
            // If you put the redirect here, it works fine...

            ViewData["ReturnUrl"] = returnUrl;
            if (ModelState.IsValid)
            {
                // This doesn't count login failures towards account lockout
                // To enable password failures to trigger account lockout, set lockoutOnFailure: true
                var result = await _signInManager.PasswordSignInAsync(model.Email, model.Password, true, false);
                if (result.Succeeded)
                {
                    if (Url.IsLocalUrl(returnUrl))
                    {
                        return RedirectToLocal(returnUrl);
                    }
                    else
                    {
                        return RedirectToAction("Index", "Home");
                    }
                }
                else
                {
                    ModelState.AddModelError("Generic", "Invalid login attempt.");
                    return View(model);
                }
            }

            // If we got this far, something failed, redisplay form
            return View(model);
}