I am running it wired.
Sorry, I did not read your post carefully. I thought your temperature was going OFL, not wind chill.
According to the manual, the lowest temp allows is -21.8F. They may be applying a range check on all temperature readings. If it goes below that value, OFL might be displayed.
You said publisher was displaying the value Ok. If that is true, it is reading from the currdat.lst file output by Heavyweather, so Heavyweather is also reading the value from the console correctly (or computing it).
It is strange, but if it is a console only issue, it is not a big deal.