Missing 4xx log entries when compared to the hrsp_4xx metric


I am observing a pattern of a large increase in value of hrsp_4xx without matching log entries.

Observing the stats I noticed that the hrsp_4xx metric is increased every 5-6 minutes by the value of 70+. In between these bumps, other values do have a corresponding 4xx log entry. When compared to the backend stats I can only match 4xx entries between these unexplained bumps.

How can I debug to determine which events are causing these increases of hrsp_4xx?

Example graph: