After having a power-outage which currepted my MySQL database, HASS (the recorder component) failed to keep logging what happens. It ran with this state for a whole day without me noticing that no data is being saved.
It would have been useful to either see a persistent notification in the HASS UI, or even better, I were able to notify myself about such serious failures.
Related issue with traceback can be found here: 4806 (closed, since it’s not really an issue)