Web frontend HomeAssistant Yellow shows "Loading Data" forever since 2025.12.0

I have access to serial. I tried to restore recent backups with no success.
What are the steps to limit number of components that can fail?
Can I clear the configuration.yaml?

HA CORE LOGS shows:


    return template.render(**kwargs)
           ~~~~~~~~~~~~~~~^^^^^^^^^^
  File "/usr/local/lib/python3.13/site-packages/jinja2/environment.py", line 1295, in render
    self.environment.handle_exception()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/usr/local/lib/python3.13/site-packages/jinja2/environment.py", line 942, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "<template>", line 1, in top-level template code
  File "/usr/src/homeassistant/homeassistant/helpers/template/__init__.py", line 1554, in forgiving_float_filter
    raise_no_default("float", value)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/helpers/template/helpers.py", line 24, in raise_no_default
    raise ValueError(
    ...<2 lines>...
    )
ValueError: Template error: float got invalid input 'unknown' when rendering template '{{(( ((states('sensor.esp_ebus_yield_total_energy'))|float)+ ((states('sensor.eastron_sdm_import_active_energy'))|float)) / ((states('sensor.eastron_sdm_import_active_energy'))|float)) | round(1)}}' but no default was specified

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/helpers/template/__init__.py", line 579, in async_render_to_info
    render_info._result = self.async_render(  # noqa: SLF001
                          ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
        variables, strict=strict, log_fn=log_fn, **kwargs
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/usr/src/homeassistant/homeassistant/helpers/template/__init__.py", line 463, in async_render
    raise TemplateError(err) from err
homeassistant.exceptions.TemplateError: ValueError: Template error: float got invalid input 'unknown' when rendering template '{{(( ((states('sensor.esp_ebus_yield_total_energy'))|float)+ ((states('sensor.eastron_sdm_import_active_energy'))|float)) / ((states('sensor.eastron_sdm_import_active_energy'))|float)) | round(1)}}' but no default was specified
2025-12-06 06:59:00.060 ERROR (MainThread) [homeassistant.components.template.template_entity] TemplateError('ValueError: Template error: float got invalid input 'unknown' when rendering template '{{(( ((states('sensor.esp_ebus_yield_total_energy'))|float)+ ((states('sensor.eastron_sdm_import_active_energy'))|float)) / ((states('sensor.eastron_sdm_import_active_energy'))|float)) | round(1)}}' but no default was specified') while processing template 'Template<template=({{(( ((states('sensor.esp_ebus_yield_total_energy'))|float)+ ((states('sensor.eastron_sdm_import_active_energy'))|float)) / ((states('sensor.eastron_sdm_import_active_energy'))|float)) | round(1)}}) renders=4>' for attribute '_attr_native_value' in entity 'sensor.scop_hp'
2025-12-06 06:59:00.063 ERROR (MainThread) [homeassistant.helpers.event] Error while processing template: Template<template=({% if (states('sensor.eastron_sdm_total_power')|float) > 1.0  %}
  {{(((((states('sensor.esp_ebus_supply_temp'))|float)-((states('sensor.esp_ebus_return_temp'))|float)) *
  (0.001163*(states('sensor.esp_ebus_water_throughput'))|float))/((states('sensor.eastron_sdm_total_power'))|float))|round(3) }}
{% else %} 0.0 {% endif %}) renders=2>
Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/helpers/template/__init__.py", line 1551, in forgiving_float_filter
    return float(value)
ValueError: could not convert string to float: 'unknown'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/helpers/template/__init__.py", line 461, in async_render
    render_result = render_with_context(self.template, compiled, **kwargs)
  File "/usr/src/homeassistant/homeassistant/helpers/template/context.py", line 45, in render_with_context
    return template.render(**kwargs)
           ~~~~~~~~~~~~~~~^^^^^^^^^^
  File "/usr/local/lib/python3.13/site-packages/jinja2/environment.py", line 1295, in render
    self.environment.handle_exception()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/usr/local/lib/python3.13/site-packages/jinja2/environment.py", line 942, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "<template>", line 3, in top-level template code
  File "/usr/src/homeassistant/homeassistant/helpers/template/__init__.py", line 1554, in forgiving_float_filter
    raise_no_default("float", value)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/helpers/template/helpers.py", line 24, in raise_no_default
    raise ValueError(
    ...<2 lines>...
    )
ValueError: Template error: float got invalid input 'unknown' when rendering template '{% if (states('sensor.eastron_sdm_total_power')|float) > 1.0  %}
  {{(((((states('sensor.esp_ebus_supply_temp'))|float)-((states('sensor.esp_ebus_return_temp'))|float)) *
  (0.001163*(states('sensor.esp_ebus_water_throughput'))|float))/((states('sensor.eastron_sdm_total_power'))|float))|round(3) }}
{% else %} 0.0 {% endif %}' but no default was specified

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/helpers/template/__init__.py", line 579, in async_render_to_info
    render_info._result = self.async_render(  # noqa: SLF001
                          ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
        variables, strict=strict, log_fn=log_fn, **kwargs
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/usr/src/homeassistant/homeassistant/helpers/template/__init__.py", line 463, in async_render
    raise TemplateError(err) from err
homeassistant.exceptions.TemplateError: ValueError: Template error: float got invalid input 'unknown' when rendering template '{% if (states('sensor.eastron_sdm_total_power')|float) > 1.0  %}
  {{(((((states('sensor.esp_ebus_supply_temp'))|float)-((states('sensor.esp_ebus_return_temp'))|float)) *
  (0.001163*(states('sensor.esp_ebus_water_throughput'))|float))/((states('sensor.eastron_sdm_total_power'))|float))|round(3) }}
{% else %} 0.0 {% endif %}' but no default was specified
2025-12-06 06:59:00.075 ERROR (MainThread) [homeassistant.components.template.template_entity] TemplateError('ValueError: Template error: float got invalid input 'unknown' when rendering template '{% if (states('sensor.eastron_sdm_total_power')|float) > 1.0  %}
  {{(((((states('sensor.esp_ebus_supply_temp'))|float)-((states('sensor.esp_ebus_return_temp'))|float)) *
  (0.001163*(states('sensor.esp_ebus_water_throughput'))|float))/((states('sensor.eastron_sdm_total_power'))|float))|round(3) }}
{% else %} 0.0 {% endif %}' but no default was specified') while processing template 'Template<template=({% if (states('sensor.eastron_sdm_total_power')|float) > 1.0  %}
  {{(((((states('sensor.esp_ebus_supply_temp'))|float)-((states('sensor.esp_ebus_return_temp'))|float)) *
  (0.001163*(states('sensor.esp_ebus_water_throughput'))|float))/((states('sensor.eastron_sdm_total_power'))|float))|round(3) }}
{% else %} 0.0 {% endif %}) renders=4>' for attribute '_attr_native_value' in entity 'sensor.cop_nu'
2025-12-06 06:59:12.006 WARNING (MainThread) [aioesphomeapi.reconnect_logic] Can't connect to ESPHome API for slaapkamerlampaj.local: Timeout while resolving IP address for ['slaapkamerlampaj.local'] (ResolveTimeoutAPIError)
2025-12-06 06:59:30.667 WARNING (MainThread) [homeassistant.components.sensor] Entity sensor.victron_max_cell_temperature (<class 'homeassistant.components.mqtt.sensor.MqttSensor'>) is using native unit of measurement 'None' which is not a valid unit for the device class ('temperature') it is using; expected one of ['°F', 'K', '°C']; Please update your configuration if your entity is manually configured, otherwise create a bug report at https://github.com/home-assistant/core/issues?q=is%3Aopen+is%3Aissue+label%3A%22integration%3A+mqtt%22
2025-12-06 06:59:30.703 WARNING (MainThread) [homeassistant.components.sensor] Entity sensor.victron_min_cell_temperature (<class 'homeassistant.components.mqtt.sensor.MqttSensor'>) is using native unit of measurement 'None' which is not a valid unit for the device class ('temperature') it is using; expected one of ['°F', 'K', '°C']; Please update your configuration if your entity is manually configured, otherwise create a bug report at https://github.com/home-assistant/core/issues?q=is%3Aopen+is%3Aissue+label%3A%22integration%3A+mqtt%22
2025-12-06 07:00:00.484 WARNING (MainThread) [homeassistant.components.automation] Error evaluating condition in 'ZonneplanPositievePrijs':
In 'condition' (item 2 of 2):
  In 'state':
    In 'state' condition: unknown entity switch.inverter_none
2025-12-06 07:01:00.529 WARNING (MainThread) [homeassistant.components.automation] Error evaluating condition in 'ZonneplanPositievePrijs':
In 'condition' (item 2 of 2):
  In 'state':
    In 'state' condition: unknown entity switch.inverter_none
#

Try to start in safe mode first.

How do you restart in safe mode if the UI doesn’t work?
via cli: ha core restart --safe-mode

i found the problem. After removing the recorder section from configuration.yaml, it seems to work again.

Depends on your installation method. Are you running the deprecated HA Core method?

Good, but you probably need to fix that section.