Hi,
The recent upgrade was to address in part an injection vulnerability. Rolling back reintroduces that vulnerability. An option while waiting on the next fix is comment out the script responsible for the select overlay.
In the woocommerce plugin folder:
includes/class-wc-frontend-scripts.php
approx. line 118 – comment out
//self::register_script( 'select2', $assets_path . 'js/select2/select2' . $suffix . '.js', array( 'jquery' ), '3.5.2' );