Just FYI I fixed it in core/um-fields.php
if ( isset( $data['allowclear'] ) && $data['allowclear'] == 0 ) {
$class = 'um-s2';
} else {
$class = 'um-s1';
}
I changed $class = 'um-s1';
to $class = ' um-s1';
The rendered output was not putting a space between the um-iconed and um-s1 classes on the select