I have a monitor of type Execute Process. On that process, I do not want to check it if another monitor, which is of type check process, is down. So, in the box labelled "Don't check if monitor is down", I put the check process monitor. After I do that, it forever thinks the execute process monitor is down, even though the other process clearly shows always up (it checks a MySQL replication slave instance). As soon as I remove the dependency in that box, both show up.
So, it seems like perhaps the don't check if down is actually checking don't check if up perhaps?
It confused me for a long time as when I get into the main screen which shows the status of all monitors, they all show up, when I bring up the execute process monitor, it also shows up, yet, the history always showed down. Took me a while to see that the issue was the dependency box.