301 redirect to external site in header aspx with RouteCollection

Question

What I'm trying to accomplish:

Add a 301 redirect to the route collection to an external site. I think I'm not fully redirecting as I'm still getting the base domain in the route for some reason. For instance, if I'm redirecting to https://google.com and my site name is https://example.com. My redirection is: example.com/https://google.com. Before marking this as a duplicate please consider the "Other stack posts suggested" section at the bottom.

What error I'm getting:

A potentially dangerous Request.Path value was detected from the client (:).

Note: I don't believe this character is the problem because the base domain shouldn't be included in the url, and I have seen this thread.

What I'm trying:

On Application_Start() in Global.aspx I define a set of 301 redirects and add them to the RouteTable.Route that property is just a RouteCollection. I add to those external routes to my RouteCollection like this:

public static void RegisterRoutes(RouteCollection routes)
{
    ...
    //inside foreach, inside condition if the redirect is external, this hits put many conditional breakpoints here
    routes.Add("Redirect" + redirect.redirect_id.ToString() + "Route", 
                    new Route(redirect.old_path, new CustomRouteHandler("~/file/full-redirect.aspx")));
    ...
}

My CustomRouteHandler class is defined as:

public class CustomRouteHandler : IRouteHandler
{
    public CustomRouteHandler(string strVirtualPath)
    {
        this.VirtualPath = strVirtualPath;
    }

    public string VirtualPath { get; private set; }

    public IHttpHandler GetHttpHandler(RequestContext requestContext)
    {
        var page = BuildManager.CreateInstanceFromVirtualPath(VirtualPath, typeof(Page)) as IHttpHandler;
        return page;
    }
}

My full-redirect.aspx.cs redirect logic is defined as:

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            DataRow dtRedirect = **query is here**;
            //if you need extra query details I use Request.Path.ToLower().Substring(1) and where clause looking for the old path. This works in all other cases.
            string newPath = dtRedirect["new_path"].ToString();
            Response.Status = "301 Moved Permanently";
            Response.AppendHeader("Location", newPath);
        }
    }

Other stack posts suggested:

• I've reviewed this thread
• Response.Redirect(newPath): I tried this and received the same result.
• Response.RedirectPermanent(newPath): I tried this and received the same result.
• Setting the Response.StatusCode to 301 along with appending the header.
• Setting Response.Redirect, StatusCode, and appending the header.
• Setting Response.RedirectPermanent, StatusCode, and appending the header.