Mautic 6.x – Forms preview and submit return 500 with no logs generated

Product Support
,
1

Your software
My Mautic version is:v6.0.7
My PHP version is: 8.3.28
My Database type and version is: 10.6.24-MariaDB-ubu2204

Your problem
My problem is: Mautic 6.x – Forms preview and submit return 500 with no logs generated

Hi,
I’m running Mautic 6.x in Docker behind Cloudflare (HTTPS) and I’m facing a persistent 500 Internal Server Error when:

  • previewing forms (/s/forms/preview/{id})

  • submitting forms (both embedded and UI preview)

The issue occurs before form validation and independently of the fields used.

Key details:

  • No log file is created in the configured log directory (var/logs)

  • prod.log is not generated at all

  • The path configured in System Settings → Path to the log directory exists (or is created) and is writable

  • Cache has been cleared

This looks like a Symfony session / CSRF / filesystem issue rather than a form configuration problem.

Questions:

  1. In Mautic 6 Docker deployments, what is the expected value and location for:

    • kernel.logs_dir

    • PHP session.save_path

  2. Are there known issues in Mautic 6 where:

    • invalid or unwritable kernel.logs_dir

    • or session storage problems
      cause silent 500 errors with no logs, especially on form preview/submit?

  3. Is there a recommended configuration for:

    • sessions

    • CSRF

    • filesystem permissions
      when running behind Cloudflare / reverse proxy?

Any guidance on the correct logging and session setup for Mautic 6 in Docker would be appreciated.

Thanks
Chapa

2

You’re losing yourself… kernel logs won’t show you anything related with a web app. It’s dedicated to the kernel.

But if you really want to waste time on that, head to the /var/log/ directory (as root).

Otherwise, the logs that you’re looking for will be generated by the web server and not by the web app.

All the other questions are pure operating system questions and unrelated with a PHP web app (you won’t find much help here on that topic. AFAIK, we’re only a few SysOp here visiting this forum).

With that said, if you’re planning to make the app publicly available, I would highly recommend you to stay away from managing your own server. And go with a shared hosting where a qualified SysOp will take care of the operating system configuration.

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