Hi,
first, thanks for this great project. The raspberry stats are very useful in Signalk.
However the path "environment.rpi.sd.utilisation" shows just NaN.

First analysis when executing the stored command

df / | grep -v Used | awk '{print $5}' |awk 'gsub("%","")' (after removing the escaping character "")

in Terminal, the following output is shown:

Verw
71

This might be connected to the 'de_DE.UTF-8' locale I'm using, but it seems like the title column is not removed and therefore a type casting from string to int fails.

Raspbian stats (cat /etc/os-release):

PRETTY_NAME="Raspbian GNU/Linux 10 (buster)"
NAME="Raspbian GNU/Linux"
VERSION_ID="10"
VERSION="10 (buster)"
VERSION_CODENAME=buster
ID=raspbian
ID_LIKE=debian
HOME_URL="http://www.raspbian.org/"
SUPPORT_URL="http://www.raspbian.org/RaspbianForums"
BUG_REPORT_URL="http://www.raspbian.org/RaspbianBugs"

Best regards
hailigsbleche