We use the Zabbix agent with over 300 clients secured by TLS with pre-shared key. With approx. 30 new devices we get the following error.
The configuration is identical to devices on which the same configuration works.
The problem exists with Zabbix Agent 5.0.14 installed via Chocolatey, 5.0.17 manually installed (MSI with OpenSSL) as well as with 5.4.7 manually installed (MSI with OpenSSL).
We also tested it with Zabbix Server 5.4.7 and Zabbix Agent 5.4.7, with the same result.
It only works with Zabbix Agent 2 on these clients with identical configuration.
We are happy to provide further information that will help to identify the problem or to give access to one of the devices for debugging purposes, e.g. via TeamViewer.
In the forum someone has the same problem: https://www.zabbix.com/forum/zabbix-troubleshooting-and-problems/424646-how-to-solve-problem-active-check-update-from-started-to-fail-ssl_write-timed-out
Zabbix Agent logs with DebugLevel=5 and configuration files attached.