When not logged in on admin on frontend sometimes the language flags dont show and the language selector dropdown is white without flags. Also when logged in on admin frontend doesnt show flags at all.
In child theme i already added two lines of code i found on WPML support because we use Siteground Optimizer.
add_filter( 'sgo_javascript_combine_exclude_all_inline', '__return_true' );
add_filter( 'sgo_javascript_combine_exclude_all_inline_modules', '__return_true' );