We battled with a similar problem for a long time, until we learnt that our dependency settings were wrong. Perhaps one possible cause. Check also that you have no downtimes set on that service…
P.S.: I assume you have the “checker” feature enabled? 
We battled with a similar problem for a long time, until we learnt that our dependency settings were wrong. Perhaps one possible cause. Check also that you have no downtimes set on that service…
P.S.: I assume you have the “checker” feature enabled?