What could be causing the "Undefined value __SitePlugin::[“Used Cars: personalize: trading-in To Text”] error in Webflow when selecting dropdown values on a form submission?

You're encountering an "Undefined value" error tied to dynamic content or a site plugin in Webflow. This usually results from integrated personalization tools or custom scripts trying to reference missing or incorrectly passed data.

1. Check Third-Party Personalization Tools

• If you're using services like RightMessage, Mutiny, or Webflow Logic with variables or personalization, ensure all expected values are defined.
• The error message suggests an internal identifier: __SitePlugin::[“Used Cars: personalize: trading-in To Text”], which looks like a personalization label or node.
• Confirm the dropdown options are properly linked to corresponding values that the personalization logic understands.

2. Verify Dropdown Field Settings

• Open the dropdown field in your Webflow Designer.
• Ensure the values are correctly set (both label and value).
• If personalization relies on a specific value from the dropdown, but that value is left blank or mismatched, it'll trigger an "undefined" state.

3. Inspect Custom Code in Page Settings

• Go to Page Settings > Custom Code (or Project Settings > Custom Code) and look for any custom scripts connected to dropdown fields.
• If there's a JavaScript snippet parsing or reacting to dropdown changes, confirm it safely handles empty or unexpected inputs.

4. Debug Using Browser Dev Tools

• Open Chrome DevTools, go to the Console tab, and reproduce the dropdown failure.
• Look for the exact script or plugin throwing that "Undefined value" error. This will help you trace whether the issue comes from:
• A Webflow Logic flow
• A third-party script
• Or a malformed CMS binding

5. Test Without Personalization

• Try publishing a duplicate version of the form/page without the personalization plugin (or with personalization disabled).
• If the issue disappears, the fault lies with how the personalization tool expects that field’s value.

6. Contact Plugin Support

• Since __SitePlugin::[...] looks like an object reference from a third-party tool, contact the plugin provider you're using for personalization, with that exact error. It’s likely they have documentation or a patch for missing field references.

Summary

The issue arises from a personalization plugin expecting a specific dropdown value that’s undefined or missing. Check your dropdown field setup, linked scripts, and any personalization logic referencing that field. Disable personalization temporarily to isolate the issue, or contact the plugin's support for a fix.