This happens when logging in or logging out
 

https://gyazo.com/e18f76aa33725fe7a721c5d14b223b9a
I'm not entirely sure what is causing it. If you hit logout / login twice it works regardless.

Well, it's an error that's as vague as it is general. From what I'm reading at StackOverflow, it may even be caused by just being on shared/free/cheap hosting if it only happens sometimes. Basically it's your database screaming "too much is happening at once" and then working fine the next time because it's not quite as busy as it had been a moment ago. :hmmm:

Huh. That's interesting. Thank you! Now I won't be panicking about it XD