I found bug #742 in version 2.0 on this address: http://redmine.pfsense.org/issues/742
We are running version 1.2.3 and experience same situation, when opt wan goes offline, and returns online after while, apinger is not aware of it.
The process is alive, but log shows down, until we restart the apinger process and restart firewall rule for loadbalance. If those 2 actions aren't done, opt wan is offline.
Our apinger binary is patched with this version found in this forum:http://www.globalmarinenet.com/downloads/wxa/apinger
Anybody managed to resolve this situation?