Problem: The client was experiencing a fatal error when trying to update a Custom Post Type with ACFML (Advanced Custom Fields Multilingual). Solution: We resolved the issue by releasing version 2.1.2 of the Advanced Custom Fields plugin, which contains the necessary fix. We recommend the client to update to this version after ensuring that they have taken a full backup of their website.
Please note that this solution might be outdated or not applicable to your case. If the problem persists, we encourage you to check the related known issues, verify the version of the permanent fix, and confirm that you have installed the latest versions of themes and plugins. If you still need assistance, please do not hesitate to open a new support ticket. For further assistance, you can reach out to us on the WPML support forum.