Yoast SEO readability analysis can provide false-positives when your display language does not match the post language

Overview of the issue

Yoast SEO supports readability analysis of your post contents.
You might get the wrong results – that your content is not passing some or all of the readability checks that they do.
This happens because while doing the analysis the current display language is being taken into account and used to process the readability score of your post.

Workaround

You can go to your user profile in Users > Profile and there select and enable the option “Set admin language as editing language.” in the “WPML language settings” section