Problem: The client is experiencing a critical error on the Arabic version of their website, which only occurs when logged in. The issue was suspected to be related to plugin compatibility. Solution: We took the following steps to diagnose and resolve the issue: 1. Updated WPML plugins to the latest version, which did not resolve the issue. 2. Updated the Meta Box AIO plugin, after which the error reappeared, indicating a compatibility issue with its latest version. 3. Rolled back WPML plugins while keeping the updated Meta Box AIO, but the error persisted. This confirmed that the problem is specifically with the latest version of the Meta Box AIO plugin. We recommend contacting the Meta Box AIO plugin author for a potential fix, as previous versions were compatible with WPML. We have temporarily reverted to an older version of Meta Box AIO to stabilize the site.
If this solution does not resolve your issue, or if it seems outdated, we highly recommend checking related known issues at https://wpml.org/known-issues/, verifying the version of the permanent fix, and confirming that you have installed the latest versions of themes and plugins. If the problem persists, please open a new support ticket at WPML support forum.