tomasJ-15

Problem:
Language switcher flag image missing alt attribute.
Solution:
Got to ../wp-content/plugins/sitepress-multilingual-cms/classes/language-switcher/ directory and edit the class-wpml-ls-model-build.php, line 190.
Remove this line:

$ret[ $code ]['flag_alt']   = ( $display_name || $display_native ) ? '' : $data['translated_name'];

And replace it with this line:

$ret[ $code ]['flag_alt']   = ( $display_name || $display_native ) ? $data['native_name'] : $data['translated_name'];

Relevant Documentation:
https://wpml.org/errata/missing-alt-tag-for-flag-image-in-a-language-switcher/