During the CSS build process, a few checks are made before the value is written. One of them is comparing the stored value against the default value. If they match, the CSS is not written, so that the file only has updated styles. This filter bypasses that check and writes the value, assuming that it exists.

Useful if another plugin's CSS is overriding your theme, and you need to ensure that the style is written out.

Ignore the default comparison check for a particular field in the CSS builder.

add_filter( 'gppro_compare_default', 'my_css_default_bypass' );
function my_css_default_bypass( $field ) {
	if ( $field === 'site-title-stack' )
		return false;