Next_alarm_sensor in companion app fails

I use the next_alarm_sensor in my companion app to start an automation. This worked very well, but since a few days the automation does not start at the time the sensor is stored in but some hours later (or earlier; I could not find out exactly yet). The next_alarm_sensor triggers a shelly1pm which switches on a pump.
Does anyone face the same problem and knows how to help?

If you don’t share any code, it’s really hard to help you.

A helper named “Protected Switch” switches on a shelly relay (running the pump). The Protected Switch is triggered either by the next_alarm_sensor (id handywecker) or by a hardware-button (shelly1mini; id tasterbadtuer).

Switching on by hardware-button works perfectly. Switching on by next-alarm_sensor worked perfectly also until the day before yesterday. Since then, switching by next-alarm_sensor fails. My first observation is that the automation does start, but at a time which differs from the time of the next_alarm_sensor (about five hours earlier?). I don’t know the reason why. I always update the shelly relays. Maybe something changed the firmware settings of the shellys?

This is the code of the automation:

- id: '1xxxxxxxxxxxxxxxxxxx'
  alias: Zirkulation mit dem Helfer Protected Switch einschalten
  description: ''
  triggers:
  - trigger: time
    at: sensor.sm_g751b_next_alarm
    weekday:
    - mon
    - tue
    - wed
    - thu
    - fri
    - sat
    - sun
    id: handywecker
  - trigger: state
    entity_id:
    - switch.shelly1minig3_xxxxxxxxxxxxxxxxxxxx
    from:
    - 'off'
    to:
    - 'on'
    id: tasterbadtuer
  conditions: []
  actions:
  - action: switch.turn_on
    target:
      entity_id: switch.protected_switch
    data: {}
  mode: single

The helper switch checks, whether the pump has run since the last 30 minutes and blocks it if yes.

Ok, here is the solution!

The solution is: companion-app - settings - manage sensors - next alarm - allow list

Check the allow list and remove all entries but “Clock” (com.sec.android.app.clockpackage). This is the only entry which must be active, all other entries must be deactivated!