Resolved
Resolved in: WPML 4.7.6
Overview of the issue
If your workflow involves editing translated posts directly (specifically, when using a page builder, which includes the core Gutenberg editor), then it is possible that when saving posts the translated content may be overwritten by the original language content.
There are two known situations where this may arise:
1. the content contains links (e.g. a page builder button with a link) and the problem happens when you save the translated post, or
2. you are working with draft posts, and you first publish the translated post, then publish the original post
Workaround
For 2. the problem can be avoided by modifying your workflow to publish the original language post before publishing the translated posts.
For 1. there is no simple workaround other than, when directly editing such translated posts (made with a page builder and containing links), temporarily disable the String Translation plugin.