Laravel Spark Subscription Sucks

Well, the Laravel's Spark subscription checkout page suddenly not working. Sounds generic right? When I try to subscribe a plan, the user created but the subscription isn't created for the user and the page redirects to local.app.name/undefined.

The spark-register-stripe vue component redirects to the Laravel\Spark\Http\Controllers\Auth\Register Controller

<?php

namespace Laravel\Spark\Http\Controllers\Auth;

use Laravel\Spark\Spark;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Auth;
use Laravel\Spark\Events\Auth\UserRegistered;
use Laravel\Spark\Http\Controllers\Controller;
use Illuminate\Foundation\Auth\RedirectsUsers;
use Laravel\Spark\Contracts\Interactions\Auth\Register;
use Laravel\Spark\Contracts\Http\Requests\Auth\RegisterRequest;

class RegisterController extends Controller
{
    use RedirectsUsers;

    /**
     * Create a new authentication controller instance.
     *
     * @return void
     */
    public function __construct()
    {
        $this->middleware('guest');

        $this->redirectTo = Spark::afterLoginRedirect();
    }

    /**
     * Show the application registration form.
     *
     * @param  Request  $request
     * @return Response
     */
    public function showRegistrationForm(Request $request)
    {
        if (Spark::promotion() && ! $request->filled('coupon')) {
            // If the application is running a site-wide promotion, we will redirect the user
            // to a register URL that contains the promotional coupon ID, which will force
            // all new registrations to use this coupon when creating the subscriptions.
            return redirect($request->fullUrlWithQuery([
                'coupon' => Spark::promotion()
            ]));
        }

        return view('spark::auth.register');
    }

    /**
     * Handle a registration request for the application.
     *
     * @param  RegisterRequest  $request
     * @return Response
     */
    public function register(RegisterRequest $request)
    {
        Auth::login($user = Spark::interact(
            Register::class, [$request]
        ));

        event(new UserRegistered($user));

        return response()->json([
            // 'redirect' => $this->redirectPath()
            'redirect' => '/thankyou'
        ]);
    }
}

How can I hack the subscription? so I can tweak it on my own.

Stripe provides really easy interface for the the subscription.