Error while saving after updates

Hello,

one of our clients is getting an error message when updating a product page. This happened after updating the WordPress version and some of the installed plugins recently. This error message states „Error while saving“. But when changes have been made on the product pages, all of them are still going through to the frontend. Meaning there is no actual error, but the message still occurs. On the blog posts or pages the error doesn’t appear.
In addition we don’t longer see messages in the backend when a page, plugin, product, etc. has been updated or deleted, like “Page updated. View page”.

We know that this error is already known, but we tried the suggested changes that have been made online and still have this error (e.g. https://wordpress.org/support/topic/unable-to-save-after-wp-5-0-upgrade/).

Then we made the following inspection:

– I’ve deactivated all plugins, except for WooCommerce.
– If I use the Twenty Nineteen theme, the editor work properly.
– When I switch to the Enfold parent theme, the error message “Error while saving” appears again.
– We then tried to update Enfold parent theme to the latest version (4.5.6), the error message “Error while saving” still appears.

Can you get in contact with me in order to have a closer look to the issue?

Best regards