Weird comportement of nagios about output of a plugin



I have took a script at nagiosexchange. The name is check_flexlm.plx.(in perl)
I have four servers with flexlm.
The script works good with three servers.
But on one server (Sun Solaris 10) , the script return 0 (it means it is good) and the good string ie "Flexlm OK"
In nagios webadmin, the text is “Flexlm OK” but the state is unknown ??
Sometimes, the state is OK.

The test is make with check_by_ssh and when i test with manual command : it always return 0 !!

Also, on three other servers (solaris too) the state is good .
Someone has an idea ?

Maybe a bug .