Calculated Number - glitching (new since core-2021.12.9)

Configuration
1

This problem only appeared since I upgraded to core-2021.12.9. I have since also upgraded to core-2021.12.10 - problem still there.

THE PROBLEM
I have two real sensors (Outside/Inside Temp), MQTT based.
I have a calculated sensor which is the difference between the two (Difference = Inside - Outside)
The calculated input is ‘glitching’ and behaving as if [Outside] is zero occasionally - even though it never is.
And because I use an Automation based on [Difference], the automation is triggering incorrectly.

DETAILS
Shown below are the raw MQTT values over a recent short interval, as seen at the MQTT broker. As can be seen - the raw data shows no cases of ‘zero’ at any time.
Indoor
Outdoor

Shown below is the calculated difference over the same period.
Notice that the Difference glitches occasionally to approx +26C which happens to be the INDOOR temp. This implies the Difference Calculation is [Indoor-0], instead of [Indoor-Outdoor]

Diff
Diff980×409 30.1 KB

YAML

- sensor:
  - name: "Diff temperature"
    unique_id: diff_temp
    unit_of_measurement: "°C"
    state: >
          {% set indoor = states('sensor.indoor_temperature') | float %}
          {% set outdoor = states('sensor.outdoor_temperature') | float %}
          {{ (indoor - outdoor) | round(1, default=0) }}

NOTE
The YAML has round(1, default=0) but the Default = 0 is NOT the problem … as if the default case was triggered, then Difference would glitch to zero … not the INDOOR temp.

Ideas???

2

Try this:

- sensor:
  - name: "Diff temperature"
    unique_id: diff_temp
    unit_of_measurement: "°C"
    state: >
          {% set indoor = states('sensor.indoor_temperature') | float(none) %}
          {% set outdoor = states('sensor.outdoor_temperature') | float(none) %}
          {{ (indoor - outdoor) | round(1, default=none) }}

This should put gaps in your graph instead of spikes.

3

But … if the default=0 was the issue, then my ‘glitches’ would show zero. They don’t.

EDIT: Just noticed this … float(none). Will try.