This type of error occurs when the database is corrupted with some entries. In order to fix it, we need to delete the specific entries that have this element ID.
Because it is database related issue, it is really important that before doing anything you backup your website and database.
Once it is done, please follow the steps here:
1. Go to WPML → Support.
2. Click on the Troubleshooting link.
3. Click on the Fix post type assignment for translations button.
Just add here, one more thing, if you can access WPML > Support tab, since you are just setting up WPML you can use the WPML reset option and reset it.