I’ve found solution to this 404 error.
Pagination links worked as expected when the Sublanguage plugin was off.
For correct pagination that works with Sublanguage though, you need to add a rewrite rule (for your links) to functions.php. After that, regenerate your permalinks (Settings > Permalinks):
function my_pagination_rewrite() {
add_rewrite_rule('your-page-name/page/?([0-9]{1,})/?$', 'index.php?pagename=your-page-name&paged=$matches[1]', 'top');
}
add_action('init', 'my_pagination_rewrite');
Thanks for the solution:
Fixing a WordPress pagination 404 error
page_slug/page/2 return 404 error
And many thanks to Maxime for this plugin.