ICMP service down but ping works fine

I have a problem in monitoring a specific node regarding ICMP: the service goes up and down continuously in OpenNMS.
When the node went down I executed a ping to that node from the server that has OpenNMS software installed and I had 0% of packets loss.
How can I solve this issue?
I’m using OpenNMS version 29.0.0-1.

Thank you

Have you tried to ping via karaf shell?