I was running 2.4.1, and I was having a flapping issue with the agent unreachable trigger. It would operate fine for hours, and then suddenly it would begin flapping on and off. This got really bad a couple of weeks ago, and so I updated the server and agents to 2.4.5.

Now I am having a worse problem. The flapping has ceased, but the false alerts have not. Now all the agents on all the hosts report unreachable at the same time, including the agent running on the server machine. This suggests an issue with the server..

The alerts do not clear until the server is restarted. The server is not overloaded, it's using about 70% of memory at most, and CPU never goes above 50%. The database is on a remote machine, and that machine is not experiencing problems either.

I wish I had more information but the server logs are not saying anything.. the problem happens once or twice or more per day, but it's not frequent so I was running the logs at level 3 instead of level 4.