Root cause

1. Bad commit: 73ef3fe99d99d34ab89dbdb89c81e9b9548dd4cb
2. Default smooth factor of 24 causes the problem

Traced this down to a faulty reference in the graph json definition. When referencing a non-existent datasource, the graph above the graph with the problem threw an error during canonicalization. This coupled with a smooth factor of 24 caused the graph to break when it was part of the dashboard: http://localhost:8081/dashboards/metrics, but not by itself: http://localhost:8081/graphs/registrations_hourly

Version: unspecified
Severity: normal