I have a few routers and switches that do OSPF routing, Juniper and Cisco. Right now I have two links down, but only the Juniper is reporting the neighbor down. The Cisco is not reporting it down as an alert, but under routing neighbors it only shows as Not Available. The Juniper shows the same thing under routing neighbors, yet I have an active alert as neighbor down. Why would that be?
I have a few other Cisco devices that do get active alerts when a neighbor is down, so not platform specific, I just don't see anything that may be misconfigured. Its the latest version of NPM too.
It sounds to me like you have some issues with OSPF neighbor adjacencies. It is possible that one end point sees it's neighbor but the reverse has a problem.
Here's a rather dry article from Cisco on OSPF Neighbor Problems if you're interested: OSPF Neighbor Problems Explained - Cisco
Good luck, and please let us know what you find.