Not sure if I’ve found an issue with the recorder and Celsius based thermostats.
I switch from the sqlite recorder because of this issue to mysql, but overnight it seems to have come back. When I look at my central heating generic thermostat it it brings up the card, but never loads the history.
I had the log running in tail, and I thin i can see it load all the entries, but I so see an error:
2019-05-22 07:26:38 ERROR (SyncWorker_19) [homeassistant.components.http.view] Unable to serialize to JSON: Out of range float values are not JSON compliant
[[<state climate.central_heating=idle; current_temperature=None, min_temp=15.0, max_temp=21.0, temperature=18.0, operation_mode=heat, operation_list=['heat', 'off'], friendly_name=Central Heating, supported_features=129 @ 2019-05-21T22:01:53+12:00>, <state climate.central_heating=idle; current_temperature=18.4, min_temp=15.0, max_temp=21.0, temperature=18.0, operation_mode=heat, operation_list=['heat', 'off'], friendly_name=Central Heating, supported_features=129 @ 2019-05-21T22:01:53+12:00>
They do look related.
Added issue on github: https://github.com/home-assistant/home-assistant/issues/24026