Sudden change of entity value (history_stats)

Hello together.
I have an entity/sensor of platform: history_stats to count duration of ‘on’ time of sauna heating. It’s been working OK until yesterday. During night it suddenly change the value - it added 88.32 to current value. I have no idea based on what it changed. Can anyone advise?

- platform: history_stats
    name: "sauna_doba_nahrivani"
    unique_id: sauna_doba_nahrivani
    entity_id: sensor.hvac_aktivita
    state: "heating"
    type: time
    start: "{{ now().replace(day=1, hour=0, minute=0, second=0, microsecond=0 ) }}"
    end: "{{ now() }}"