Title: REST-API JSON Errors & WPML Directory Duplication (/de/de/)
Last modified: May 5, 2026

---

# REST-API JSON Errors & WPML Directory Duplication (/de/de/)

 *  [ath2805](https://wordpress.org/support/users/ath2805/)
 * (@ath2805)
 * [1 week, 3 days ago](https://wordpress.org/support/topic/rest-api-json-errors-wpml-directory-duplication-de-de/)
 * Hello,
 * We are experiencing severe issues using Custom Permalinks alongside WPML and 
   the Gutenberg Editor:
 * JSON Response Error: Saving posts often fails with a “Not a valid JSON response”
   error. This seems to be a REST-API disconnect triggered during the permalink 
   calculation process.
 * URL Duplication: In multilingual setups, the language prefix is being duplicated
   in the preview URL (e.g., /de/de/your-slug/), leading to 404 errors.
 * Sync Lag: It often takes 3–4 saves for the correct permalink to be registered
   and reflected in the frontend.
 * WPML support has investigated this and confirmed that the plugin’s handling of
   the custom_permalink meta field currently conflicts with their directory-based
   language negotiation.
 * Could you please look into how the plugin hooks into the REST-API save process
   to prevent these collisions?
 * Best regards.

You must be [logged in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fwordpress.org%2Fsupport%2Ftopic%2Frest-api-json-errors-wpml-directory-duplication-de-de%2F%3Foutput_format%3Dmd&locale=en_US)
to reply to this topic.

 * ![](https://ps.w.org/custom-permalinks/assets/icon.svg?rev=1785367)
 * [Custom Permalinks](https://wordpress.org/plugins/custom-permalinks/)
 * [Support Threads](https://wordpress.org/support/plugin/custom-permalinks/)
 * [Active Topics](https://wordpress.org/support/plugin/custom-permalinks/active/)
 * [Unresolved Topics](https://wordpress.org/support/plugin/custom-permalinks/unresolved/)
 * [Reviews](https://wordpress.org/support/plugin/custom-permalinks/reviews/)

 * 0 replies
 * 1 participant
 * Last reply from: [ath2805](https://wordpress.org/support/users/ath2805/)
 * Last activity: [1 week, 3 days ago](https://wordpress.org/support/topic/rest-api-json-errors-wpml-directory-duplication-de-de/)
 * Status: not resolved