Etherpad error

I get the attached error when visiting the URL. When it's done loading, the pad appears and the error goes away. If I F5 I see it again, if I hard refresh not (?!).

In the Javascript console I have the following though:

Async statement execution returned with '10', 'disk I/O error'

So there are good chances it's a problem on my end.

Version: unspecified
Severity: normal
URL: https://etherpad.wikimedia.org/p/html_templating

Attached: