Hello Zabbix Team,

This is my first time opening a ticket here, so please bear with me if I miss anything or make any mistakes—I’m still learning the process. I also want to note that I do not have an active Zabbix support subscription, so any guidance you can provide through the community is greatly appreciated.

Summary
After upgrading both Zabbix Server and Proxy from version 7.2 to 7.4, all items generated by host prototypes consistently exhibit a critical validation bug: when editing or saving an item prototype, the Proxy field rejects the valid selection and reports

“This field cannot be empty.”

—even though the host and its items were previously monitored successfully under the same proxy. Creating or editing items manually does not reproduce this issue; it only affects items created via prototypes.

Technical Details

• Zabbix versions

• • Server: 7.4.x

• • Proxy: 7.4.x (active mode)

• Database: PostgreSQL

• Affected configuration:

• • Templates using VMware/AWS Discovery → Host prototypes → Item prototypes

Reproduction steps

1. Upgrade Zabbix Server and Proxy from 7.2 → 7.4.

1. Navigate to Configuration → Templates → Host prototypes.

1. Select any existing item prototype and click Edit.

1. Observe that the Proxy dropdown is pre-populated with the correct proxy.

1. Click Save without making any changes.

1. The form fails validation and displays:

Thank you for your time and patience. I hope this information helps diagnose and resolve the issue. Please let me know if you need any additional details or clarifications.

Best regards,