For line graphs (not stack graphs), data series without a value for a given timestamp (there is a gap in the data) still appear in the tooltip when hovering over that timestamp. Additionally, the value is shown as "0" rather than indicating that there is no value for that timestamp.
Test with payload 4.9.0-0.nightly-2021-08-07-175228 From the screenshot in #c3 we can know that data series without a value for a given timestamp didn't appear in the tooltip when hovering over that timestamp. Additionally, the value is shown as "None" to indicate that there is no value for that timestamp.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory (Moderate: OpenShift Container Platform 4.9.0 bug fix and security update), and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHSA-2021:3759