check_wmic -- UNKNOWN - Usage problem

I am using the following command:

check_wmic --host 192.168.31.10 --user a***** --password b**** --alias cpu --property LoadPercentage  --every 1 --repeat 5 --format "CPU load %.2f%.|'CPU Load'=%.2f%" --warning 85 --critical 95

When Nagwin runs the check the result is:

UNKNOWN - Usage problem 

If I run this from the command line I get the following result:

OK - CPU load 0.21%.|'CPU Load'=0.21%

Why is this failing though Nagwin?