Update: after several configuration improvements over the weekend, the error rates have stabilized close to zero, so we're closing the incident.
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Some of our users experienced increased error rates, sometimes with the error message upstream connect error or disconnect/reset before headers. reset reason: connection termination, on Thursday May 31st from 5pm to 11pm (UTC). Our engineers applied an emergency fix and the problem went away. However, the root causes of the issue and a final fix for it are still being investigated.
We're sorry for the inconveniences caused. We will keep posting updates as the investigation progresses.