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?

The "Undefined value __SitePlugin::[“Used Cars: personalize: trading-in To Text”] error in Webflow likely stems from a broken connection between a form dropdown and a custom script, CMS binding, or third-party integration.

1. Check Dropdown Field Bindings

• Ensure the dropdown options are correctly populated and linked to the Webflow CMS or form logic.
• If using static options, confirm that they match expected values from scripts or external data sources.

2. Inspect Custom Code or Third-Party Scripts

• Look for JavaScript manipulating the dropdown, as this could be failing when trying to read a selected value.
• Check the browser console (F12 > Console) for JavaScript errors. If the error is related to a missing value, update the script to handle cases where no selection exists.

3. Verify Integrations (Zapier, Make, APIs)

• If the dropdown is connected to Zapier, Make (Integromat), or an API, ensure that:
• The integration is sending/extracting the correct field values.
• Webflow’s form submission map matches what the external tool expects.

4. Check CMS Collection Logic

• If the dropdown dynamically pulls from a CMS collection, verify that:
• The underlying CMS field exists and is correctly referenced.
• The binding syntax is valid within Webflow’s designer or custom script.

5. Inspect Localization or Site Plugins

• If using Webflow’s localization options or a third-party translation plugin, inspect how dropdown data is processed.
• Some plugins append extra values, potentially causing issues when selecting dropdown items.

Summary

This error usually occurs due to missing or improperly referenced dropdown values in custom scripts, CMS bindings, or integrations. Start by checking bindings in Webflow, inspect JavaScript errors in the browser console, and verify any connected third-party services handling form data.