This thread is resolved. Here is a description of the problem and solution.
Explain the media options in WPML -> Settings -> Media Translation Especially the 'Duplicate media attachments for translations' option.
This request was sent to our documentation team, and if needed they will revise it and add the explanations to our documentation.
For the custom fields options, please see this documentation.
This is the technical support forum for WPML - the multilingual WordPress plugin.
This topic is split from https://wpml.org/forums/topic/saving-taxonomy-translation-settings-creates-new-terms-for-taxonomies/