Hello! Sorry, but I believe this is on our end. I've had a report about 4.2 as well, and I can replicate. We're getting a timeout (a 504) upon submissions, but oddly only for some challenges. I only am aware of these 2 challenges having this issue currently.
I've let developers know, but am unaware of an eta for a fix.
You can skip ahead using the ☰ button in the upper-left, and please get in touch with us in https://support.codeschool.com/help/contact-feedback as we can make sure your solution is correct (you can if you wish check out the answer in the challenge, too) and mark the course on your dashboard and report card as complete.