502 Bad Gateway
These messages are getting a bit old. It is indicative of a communication failure between servers or attempting to re-use a file in the browser's cache. Since I have my browser delete temp files whenever it is closed, with the exception of cookies, since there are some I'd like to keep (for various site settings), I would suggest addressing it at the server side.
Considering I'm not running your backend, and can determine a hald dozen possible causes off of the top of my head, I should think you can resolve it.
For the user, this message is essentially harmless, aside from being really annoying. However, since it come up in the comments every day, perhaps it is time to fix this. If you need to hire someone for the purpose, there are many qualified visitors to your site, including myself, that are "for hire"...not that I can speak for anyone else.