It's been a rough few days since upgrading to our new backend, but we've isolated and fixed the major problems involving 502s and 504s. Thanks for your patience while we sorted this out! We're also aware of some smaller issues, thanks to the new threads in the Bug Reports forum, and we're working on fixing those ASAP. As always, if something around the site doesn't seem right to you, post or comment in the Bug Reports forum so we can get everything fixed up and back to normal.
Also, give a huge round of applause to our new dev Lorentz! His very first commit to the Waffles codebase was the commit that fixed the timeout issues (though the issue was id'd by Squiz). Thanks for all your help and hard work, Lorentz.