https://github.com/mysensors/MySensors/pull/1562 switches to using libgpiod instead of the earlier interface. I have not tested it myself but it looks good.
@mvader Turn the time delay adjustment preset on your PIR module to the minimum.. Now try it.. You will not get a continuous output..Also, prepare the circuit using a long wire from the back to the sensor of your module.
I'm having the same / a simular issue of temperature related readings, but at a different temperature level (for me it must be > 14 degree). I massure the dew point as well (temperature = orange, dew point = yellow). It looks to be more related to water in the air than only to temperature.
@zboblamont have you been finally been able to find a solution?