This is a bad time for Wikidata Query Service. We had a few issues last week to update WDQS and reload all data. During this data reload, we are running on a single server. And now this server is starting to behave erratically.

I honestly do not know yet what is happening except that we see a lot of file (pipes actually) left open and that WDQS stops responding. Investigation is going on [1] and we'll let you know what we find.

Sorry for the inconvenience and thank you all for your patience!

[1] https://phabricator.wikimedia.org/T134238