Occasionally—I'd say about 30-40% of the time—when submitting a form in the backend, be it saving an entry, updating a custom field, etc, the page will just sit there, loading. This can and often does continue for ~ 299.88 seconds, after which it will proceed to the next screen as if nothing ever happened.
I've looked through the console log, but all the timestamps seem to be within a second of each other, so nothing jumps out as the step where things are getting hung up. I suspect a server problem, but I'm posting here just in case anyone can point me in a more specific direction than "there's a problem somewhere".
To date, this has not occurred on the frontend, but there aren't any frontend forms to submit, either.
Pastebin of the console log (the load time is on line 725): https://pastebin.com/aB4JkrBv