Not really a great bug report but... Jenkins stopped casting its +1/-1 Verified votes on Gerrit, despite the builds working fine, and I see no errors either in Gerrit's log or Jenkins' log, but the jenkins/manage page says

The Gerrit-trigger send commands queue contains 127 items!
Something might be stuck, or your system can't process the commands fast enough. Try to increase the number of sending worker threads on the Gerrit configuration page.

How can we troubleshoot what's wrong, knowing that nothing has changed recently and things have been up and working for a while?