zabbix-agent2 seems to hang sometimes and needs to be force-killed (SIGKILL) and restarted via systemd. I noticed this behavior on several machines and I could not find out the exact problem.

Steps to reproduce:

1. Install zabbix-agent2 from repos
2. Configure passive checks using PSK from one zabbix server
3. collect data and wait for 1-2 days
4. Inspect "Agent ping" graph to find out when the issue pops up

Result:

• Metrics are missing for short intervals (not just agent pings!)
• systemctl restart zabbix-agent2 hangs
• kill -9 $(pidof zabbix_agent2) followed by a service restart is required

Expected:

• Stable agent pings and metrics