Steps to reproduce:
- Import the Template with self-customized discovery rule.
- Update the discovery rule grahp prototype to use Stacked graph type.

- Go back to All Template, and export the template.

- Then report Page not found.
- I try to use the Normal graph type to export the template, it is working.
Result:
See screenshot

When this error occured, I didn't see any logs printing in /var/log/zabbix/.log and no any error logs about this in /var/log/php-fpm/.log and in /var/log/httpd/*.log.
Zabbix Version
zabbix_server (Zabbix) 7.4.6 Revision 626d2b8a482 17 December 2025, compilation time: Dec 17 2025 00:00:00 Copyright (C) 2025 Zabbix SIA License AGPLv3: GNU Affero General Public License version 3 <https://www.gnu.org/licenses/>. This is free software: you are free to change and redistribute it according to the license. There is NO WARRANTY, to the extent permitted by law. This product includes software developed by the OpenSSL Project for use in the OpenSSL Toolkit (http://www.openssl.org/). Compiled with OpenSSL 3.2.2 4 Jun 2024 Running with OpenSSL 3.5.1 1 Jul 2025
Expected:
Export the template in different format successfully