I had a situation where there was a space character that crept into my menu URL links before the final language parameter somehow, and then sub-menu item links were broken. After much research I discovered that Astroid had a template override in mod_menu, the default_component.php file. For some reason the developers discarded the Joomla default link filtering. To fix it, I replaced line 88 and restored the URL filter.
echo '<a href="'.$item->link.' " title="'.$item->title.'"> <span class="nav-title">'.$iconHtml.$item->title.$badgeHtml.'</span>'.$subtitle.'</a>';
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