I created a 'Test' trigger that is using zabbix agent ping item:

{Template App Zabbix Agent:agent.ping.last(0)}=1

This creates a PROBLEM as it should.

I change the trigger to:

{Template App Zabbix Agent:agent.ping.last(0)}=2

I never receive an OK.

Another scenario:

Using an older Zabbix Appliance with version 2.0.0 and MySQL:

I modify the "Too many processes on Zabbix server" trigger to:

{Zabbix server:proc.num[].last(0)}>50

This created a PROBLEM event.

I modify the trigger again with:

{Zabbix server:proc.num[].last(0)}>500

I never receive an OK event.