Hosts randomly switching to "Unknown" while data collection still works

[sparkly]

Hello everyone,

I am currently facing a strange issue with Zabbix where the agent interface of hosts randomly switches to "Unknown".

What is confusing is that:

• The hosts are still sending fresh data.
• Triggers continue to fire correctly.
• Metrics are updated normally.

So communication between proxy and agents still seems to work.

The issue can temporarily be resolved by:

• Restarting the Zabbix proxy
• Or disabling and re-enabling the affected hosts

Environment


The infrastructure is identical for all customers:

• 2 physical servers per customer
• Around 7 hosts per customer in Zabbix
• All hosts monitored through a proxy

Versions

• Zabbix Server/Proxy version: 7.4.10
• Zabbix Agent versions: 7.4.7 - 7.4.10
• Zabbix agents versions: 7.2.12 - 7.4.10

At the beginning, the issue appeared randomly and usually affected all 7 hosts of a single customer at once.

However, during the last two days, the problem escalated:

• All 46 monitored hosts became "Unknown" overnight.

Troubleshooting done

• I checked both proxy logs and agent logs.
• I could not find any related errors or warnings.
• On Sunday, I configured the proxy service to restart automatically at 5:00
• Yesterday and today at 08:00 all hosts were still / already unavailable/unknown.
• According to the proxy status, the service had already been running for 3 hours, so the restart itself worked correctly.
• After manually restarting the proxy again at 08:00, all hosts immediately became available again.

Has anyone experienced similar behavior or has ideas what could cause this?

Thanks in advance.