On several of our Solaris 10 systems the time it takes to get a proc.num value spikes to several seconds. Often taking so long the server gives an error

Zabbix agent item [proc.num[]] on host [xxxx] failed: first network error, wait for 15 seconds

Doing some testing with zabbix_get it usually takes under 5 ms, but regularly spikes to several seconds. These systems are roughly 90% CPU idle.