502 Bad Gateway errors and FTP Unavailable

What hosting volume are your websites on?

If your server wasn’t already upgraded to PHP 8.2, I am suspecting it might be now:

Seeing how similar issues have affected this particular group of servers in the past, one could speculate that they may belong to the same server cluster, or server clusters with similar configuration.
We know that one server hadn’t been upgraded yet, and the upgrade was expected to be carried out in these days. This could be a reason for this error; but they also could be facing an entirely different issue. We don’t know for sure, yet.