So, here my findings – there are indeed two other plugins that trigger 'get_user_locale()' too early, but still – they do not cause the issue with BNFW. Even when I disable them and BNFW becomes the first to call 'get_user_locale' (I’m setting a breakpoint to check who gets there first) – I still see the wrong language loaded as it happens too early on BNFW load.
I permitted myself the freedom to temporarily alter your code, namely – I changed the bnfw.php 'load_textdomain' function, by putting the 'load_plugin_textdomain' function in the WP 'init' action like this :
public function load_textdomain() {
// Load localization domain.
$this->translations = dirname( plugin_basename( FILE ) ) . '/languages/';
add_action('init', function() {
load_plugin_textdomain( 'bnfw', false, $this->translations );
});
}
Now, this works perfectly fine at first glance, but I did it only as a proof of concept. I’m not sure if it is actually the proper thing to do in order to fix this, but I hope it gives you some direction on what is happening and how it can be fixed eventually. Unfortunately – I couldn’t sort out any particular reason why it is fine at your place and works wrong at mine.
