MR performance sparkline deploy indicator is not accurate

I'm not sure if this is a CI problem or a Prometheus problem, but the ball to indicate the deployment on the sparkline isn't working. Note it should almost always be in the middle of the chart, since it is supposed to show 30min before/after. This did use to work, but not it appears to be broken.

Note the other aspects of the sparkline seem to be fine, you can see in this image the dip in values which would be when then deploy occurred.