That’s related to netdata, because it can’t read the value. You can disable in it.
The best way, how you can do it is download netdata.conf, which you can download from here http://192.168.1.1:19999/netdata.conf and replace it in your router /etc/netdata/netdata.conf
In the replaced file, you need to uncomment and change the value of it.
There you can see:
# /sys/fs/btrfs = yes
Uncomment it by just deleting the # and instead of yes, write there no.
So, in the end, it will look like this:
/sys/fs/btrfs = no
Restart netdata and errors from the netdata are gone.