Our site was hit with an extremly slow backend and 502 errors for every action (deactive plugins, create coupon, delete customer, create a post, basically every random action you could do in the backend).
Logged in customers were not able to check out. Every logged in customer experienced 502 errors in checkout for all ajax-tasks.
Together with the hosting support we found out Multilingual CMS was causing the issue. A XRAY shows this.
Reactivating it directly causes 502 errors again, the first one shown directly after reactivation.
I tested it five times. Issue only occurs with Multilingual & Multicurrency active.
We now rolled back to an older version and the issue persists. After you activate Multilingual CMS, the checkout is throwing 502 erros, the backend gets extremly slow and is also showing 502 errors on every action.
You can find the XRAY PDF file from the hoster here:
Technical Support Summary: Critical Performance Bottleneck
Issue: Severe backend latency (requests exceeding 16 seconds) leading to immediate 502 Bad Gateway errors via Cloudflare. This specifically breaks AJAX processes, such as the WooCommerce checkout for logged-in users.
Key Findings from X-Ray Monitoring:
Primary Bottleneck: The WPML (sitepress-multilingual-cms) plugin is responsible for 42.77% of the total execution time, adding roughly 7.19 seconds of overhead per request.
External API & API Logic: A significant portion of the load is tied to external calls via curl_exec (15.85%).
CachedATEAPI.php Impact: The report specifically identifies delays in call_user_func_array linked to WPML's CachedATEAPI.php, indicating that communication with the Advanced Translation Editor is a major factor in the slowdown.
Database Stress: WPML introduces heavy queries involving the wp_icl_translations table, which adds significant processing time even to standard functions like counting comments or loading navigation menus.
Secondary Load Factors: Other notable contributors include Query Monitor (15.39%) and Object Cache Pro (7.26%).
Conclusion:
The system is currently timing out because WPML’s internal logic and external API calls (specifically the ATE API) are taking too long to respond. This pushes the total request time beyond Cloudflare’s gateway limits, causing the 502 errors.
Thank you for contacting WPML support. I’d be happy to assist you with this issue.
Thank you as well for the detailed information. Since WPML is a multilingual plugin, it needs to connect and manage all available resources on your site to support multiple languages. Because of this, a resource increase of around 10–20% is expected. However, in your case, the increase appears to be significantly higher.
From the debug information you shared, I noticed that you are using PHP version 8.4.18. I recommend downgrading to PHP 8.3, as WPML is still being optimized for full compatibility with PHP 8.4.
Additionally, resource usage can sometimes be affected by conflicts between plugins. To help identify the root cause, I suggest the following steps:
- Create a staging site so we can safely test without affecting the live site
- Temporarily disable all non-WPML-related plugins and switch to a default theme, then repeat the same actions to check if the issue persists
