This thread is resolved. Here is a description of the problem and solution.
Problem: Update Failed: undefined
Solution: 1. Please take your full site backup.
2. Deactivate the existing WPML plugin.
3. Delete the plugin files – this does not delete your translations. You will simply delete the plugin files from your "wp-content/plugins" folder, NOT the database records.
4. Download the updated plugins from our servers (https://wpml.org/account/downloads/) and upload them to the plugin directory.
5. Activate the WPML plugin and add-ons.
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