Good job

Your script works ok, tested against a Riello UTM410K (with a netman 204 card).

The only bug I’ve found is on line 660, when you check for Warning/Critical threshold, my bash return an error due to the fact that you ask for a range (x:y) rather than a simple integer.

I would suggest to change the IF condition to

if [[ -z $WARNING ]] | [[ -z $CRITICAL ]]; then