core: EDL21-Sensor stops working after a while

The problem

The “edl21”-Sensor stops working after 2-3 days of working normally. I don’t know why this happend. After restart of HA it is working again for 2-3 days.

What version of Home Assistant Core has the issue?

core-2022.7.7

What was the last working version of Home Assistant Core?

core-2022.7.7

What type of installation are you running?

Home Assistant OS

Integration causing the issue

edl21

Link to integration documentation on our website

https://www.home-assistant.io/integrations/edl21/

Diagnostics information

No response

Example YAML snippet

sensor:
  - platform: edl21
    name: Stromzaehler
    serial_port: /dev/ttyUSB0

Anything in the logs that might be useful for us?

Error adding entities for domain sensor with platform edl21

Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/helpers/entity_platform.py", line 397, in async_add_entities
    await asyncio.gather(*tasks)
  File "/usr/src/homeassistant/homeassistant/helpers/entity_platform.py", line 552, in _async_add_entity
    unit_of_measurement=entity.unit_of_measurement,
  File "/usr/src/homeassistant/homeassistant/components/sensor/__init__.py", line 372, in unit_of_measurement
    native_unit_of_measurement = self.native_unit_of_measurement
  File "/usr/src/homeassistant/homeassistant/components/edl21/sensor.py", line 457, in native_unit_of_measurement
    return SENSOR_UNIT_MAPPING[unit]
KeyError: 'Hz'

Error doing job: Task exception was never retrieved
Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/helpers/entity_platform.py", line 397, in async_add_entities
    await asyncio.gather(*tasks)
  File "/usr/src/homeassistant/homeassistant/helpers/entity_platform.py", line 552, in _async_add_entity
    unit_of_measurement=entity.unit_of_measurement,
  File "/usr/src/homeassistant/homeassistant/components/sensor/__init__.py", line 372, in unit_of_measurement
    native_unit_of_measurement = self.native_unit_of_measurement
  File "/usr/src/homeassistant/homeassistant/components/edl21/sensor.py", line 457, in native_unit_of_measurement
    return SENSOR_UNIT_MAPPING[unit]
KeyError: 'Hz'

Additional information

SmartMeter: APATOR Norax 3D